Labour and the Conservatives have sought to blame each other for the release of the convicted terrorist who killed two people in London Bridge on Friday.
Prime minister Boris Johnson and home secretary Priti Patel both claimed that Jeremy Corbyn’s party was responsible for the law that meant 28-year-old Usman Khan was freed on licence half way through his 16-year sentence.
Meanwhile former shadow home secretary Yvette Cooper questioned what action the government took to assess the risks posed by the attacker, and both Labour leader Jeremy Corbyn and Sadiq Khan, the mayor of London, pointed to cuts made to public services over the last decade.
Mr Khan, who was convicted of terrorism offences in 2012 and released last December, was fatally shot by police at about 2pm on Friday. One of the victims has been named as 25-year-old Jack Merritt, who worked as a course coordinator for the prisoners’ rehabilitation programme holding the event at Fishmongers’ Hall.
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Meanwhile Boris Johnson says his government would bring in minimum prison sentences of 14 years for convicted terrorists.
He also wants to prevent early release for anyone convicted of terrorism and extremist offences.
Mr Johnson added: "This system has got to end - I repeat, this has got to end, as I've been saying for four months. If you are convicted of a serious terrorist offence, there should be a mandatory minimum sentence of 14 years - and some should never be released.
"Further, for all terrorism and extremist offences the sentence announced by the judge must be the time actually served - these criminals must serve every day of their sentence, with no exceptions.
"These simple changes, in line with what I've been saying since becoming Prime Minister, would have prevented this attack.
"I believe they will help stop further attacks and these changes will be made urgently in the New Year if I am Prime Minister and have a majority in Parliament."
Jeremy Corbyn says he will back the police use of lethal force to protect lives, according to the same speech.
After paying tribute to the police and members of the public who responded to the London Bridge attack, the Labour leader is expected to say:
I will always do whatever is necessary and effective to keep our people safe.First of all, the police who put themselves on the line to protect us will have the authority to use whatever force is necessary to protect and save life.If police believe an attacker is wearing a suicide vest and innocent lives are at risk, then it is right they are able to use lethal force.
Earlier this month he was criticised for saying it would have been "the right thing to do" to capture Isis leader Abu Bakr al-Baghdadi alive, if possible, and put him before the International Criminal Court.
Boris Johnson accused him of being "naive to the point of being dangerous".
Targeting the Conservatives over cuts to public services over the past decade, Jeremy Corbyn will also argue that "you can't keep people safe on the cheap".
He will say during the speech in York on Sunday: "It is our duty to look calmly and seriously at what we need to do to give people real security. Our public services are the glue that bind our society together.
"Community policing, the probation service, mental health, youth and social services, all play a vital part.
"When those public services are cut back as they have been during the past decade, they leave behind gaps.
"That can lead to missed chances to intervene in the lives of people who go on to commit inexcusable acts, whether it's during their childhood, their first brush with the law, their first conviction, or in prison through rehabilitation programmes.
"Take the probation service, part-privatised in 2014, resulting in disaster. The most serious cases stayed in a justice system badly undermined by austerity. A failure to recruit has left huge staffing shortfalls and with staff supervising more cases than ever expected, posing a serious risk to our security.
"Real security doesn't only come from strong laws and intelligence, it comes also from effective public services that have the funding they need. You can't keep people safe on the cheap."
Jeremy Corbyn has launched an attack on previous political leaders in the UK for fuelling the threat of terrorism by "making the wrong calls" about the nation's security..
In a speech he is due to give in York on Sunday, two days after the London Bridge attack, the Labour leader will say that the "war on terror" has failed.
Mr Corbyn will point out that he warned against the invasion and occupation of Iraq 16 years ago, adding: "I said it would set off a spiral of conflict, hate, misery, desperation that will fuel the wars, the conflict, the terrorism, and the misery of future generations. It did, and we are still living with the consequences today."
He will go on to say: "For far too long, our country's leaders have made the wrong calls on our security. Their mistakes in no way absolve terrorists of blame for their murderous actions. The blame lies with the terrorists, their funders and recruiters.
"But if we are to protect people we must be honest about what threatens our security. The threat of terrorism cannot and should not be reduced to questions of foreign policy alone. But too often the actions of successive governments have fuelled, not reduced that threat."
He is also expected to argue that Britain should free itself from US influence - describing Boris Johnson as "the world's leading sycophant" towards Donald Trump.
Mr Corbyn will say: "Real security requires calmly making the right calls at moments of high pressure, often against the grain of conventional wisdom.
"That requires the courage and strength to chart an independent course when we think our friends and allies are doing the wrong thing.
"It is time for Britain to stop being tied to Donald Trump's coat-tails. Boris Johnson has been the world's leading sycophant towards the US President.
"From climate change denial to unconditional support for the Israeli far right, from racism to confrontation with China, Trump is taking the world on a dangerous path.
"Britain must make its own foreign policy, free from a knee-jerk subservience to a US administration which repudiates our values.
"Under Labour, Britain will have its own voice in the world, standing tall for security, peace and justice. That's the path to real security."
The father of Jack Merritt has rejected attempts to blame "lenient sentences" and instead suggested the probation service - which monitors released prisoners - should be properly funded.
David Merritt also pays tribute to his son as "an exceptional young man".
Several barristers have intervened in the political debate over the release of the London Bridge attacker - to point out that both Labour and Conservatives have misunderstood the law.
They include David Anderson, the former independent reviewer of terrorism legislation, barrister Matthew Scott and the anonymous book-writing Secret Barrister, who says politicians are seeking "to exploit the tragedy for their own ends".
London Bridge attacker Usman Khan featured in a newsletter for the Learning Together programme, according to the BBC.
He is said to have thanked the education initiative for their help and for providing him with a laptop.
The Learning Together newsletter quoted "Usman" as saying: "It is more than just an organisation, helping to provide learning of individual academic subjects.
"For me it’s main benefit is bringing people together, through the means of learning. Learning Together is about opening minds, unlocking doors, and giving voice to those who are shut down, hidden from the rest of us.
"It helps to include those who are generally excluded. This is what Learning Together means to me.
"I typed these reflections on the Chromebook I received and I am truly grateful to be able to express myself through it.
"I cannot send enough thanks to the entire Learning Together team and all those who continue to support this wonderful community."
Mr Khan was invited to the Learning Together conference at Fishmongers' Hall on Friday to mark the programme's fifth anniversary.
Several academics had tweeted about the conference before the attack.
The licence conditions of every terrorist offender are being reviewed following the London Bridge attack, according to the Ministry of Justice.
A spokesman said: "Work is already advanced on reviewing the licence conditions of every terrorist offender, making sure conditions are as tough as they need to be. We are also stepping up our already frequent meetings with these offenders."
The MOJ said the review was being undertaken to "guarantee public safety rather than because of any particular concern".
Assistant Commissioner Neil Basu said earlier this evening: “Detectives and forensic officers remain at the London Bridge area and cordons continue to be in place as we meticulously gather the evidence required for the investigation and this obviously may take some time.
"We’re working as fast as we can, we would ask the public to continue to avoid the area and we really thank those affected by this for their patience and understanding."
Some more tributes to London Bridge victim Jack Merritt, including one from British rapper Dave.
As a recently released prisoner, attacker Usman Khan was being monitored by MI5 but not kept under constant surveillance, reports The Independent's defence editor Kim Sengupta.
Such monitoring involves a number of security measures rather than a target being tracked at all times.
There was no reason for a round-the-clock watch, say security officials, because there had been no intelligence to suggest that he had returned to terrorism.
London Bridge attacker was 'being monitored by MI5, but not under constant watch'
'It is very difficult to stop someone from going out and buying a knife and carrying out an attack,’ security source admitsThe attacker wrote to a specialist intervention provider for help with deradicalisation while in prison, according to his solicitor Vajahat Sharif.
Mr Sharif told the BBC that Khan wanted to "correct" himself but "the powers that be were unable to provide that assistance while he was in custody".
Islamic State has claimed the London Bridge attack on Friday was carried out by one of its fighters, according the group's Amaq news agency.
Amaq added that the attack was made in response to Islamic State calls to target countries that have been part of a coalition fighting the jihadist group. No evidence was provided to support the claim.
As politicians continue to argue about which party was to blame for Usman Khan's early release, here is a short explanation of his contact with the criminal justice system.
In December 2010, Khan and eight others were charged with conspiracy to cause explosions and other terrorism offences.
On February 1, 2012, all nine pleaded guilty to a variety of terrorist offences, with Khan admitting a lesser charge of engaging in conduct in preparation for acts of terrorism between November 1 and December 21, 2010. This related to plans for a terrorist training camp in the Kashmir region of Pakistan, including attending operational meetings, fundraising for terrorist training, preparing to travel abroad and assisting others in travelling abroad.
Khan and two others, known as the Stoke defendants, were originally given indeterminate sentences with a minimum term of eight years behind bars instead of a fixed term. The judge Mr Justice Wilkie concluded it was required to protect the public, as Khan had a "serious long-term plan" and a commitment to terrorism.
These indeterminate sentences, known as Imprisonment for Public Protection (IPPs), came into force in 2005 and were given to violent or sexual offenders who posed a risk to society. IPP prisoners would have to serve the minimum before the Parole Board could consider whether it was safe for them to be released.
The law was changed in December 2012, abolishing the IPP and replacing it with "two strikes" life sentences, or extended sentences where offenders would have to serve two-thirds of their sentence (rather than half as in other determinant sentences). This new legislation also stated that offenders given a custodial term of 10 years or more (such as in Khan's case) were referred to the Parole Board after reaching that two-thirds point..
Khan appealed against his sentence and it was quashed by the Court of Appeal in 2013 because he had been "wrongly characterised" as more dangerous than the other defendants from London who were given determinate (fixed term) sentences of imprisonment.
Mr Justice Leveson, based on the law as it applied at the time of the offence, gave Khan an extended determinate sentence of 16 years imprisonment, with an extra five years licence. This meant he would be automatically released after eight years - half way through his sentence - and then supervised by the probation service for 13 years after his release.
As a result Khan was freed in December 2018 after spending eight years in prison, including the 408 days he spent in custody before his trial.
A former head of the Metropolitan Police's counter-terrorism command has argued attacker Usman Khan should have been barred from entering central London as part of the conditions of his early release from prison.
Richard Walton also suggested longer prison terms and better deradicalisation programmes within jails are needed to help stop offenders committing attacks after they are released.
"His licence conditions should have restricted him from visiting central London," he said.
"It is unusual for terrorist prisoners who have been released to go on to commit attacks. Every case is unique and risk assessments are complex.
"The only way to be 100 per cent certain of zero risk is to keep a prisoner in prison. All forms of surveillance have limitations."
Usman Khan was freed on licence in December 2018 and was wearing an electronic monitoring tag when he launched the attack.
UK head of counter-terrorism policing Neil Basu said Khan had been subject to multi-agency public protection arrangements (MAPPA) and had complied with an "extensive list of licence conditions" following his early release.
The precise terms of Khan's release are not yet known.
The father of victim Jack Merritt had earlier said that his son "would not wish his death to be used as the pretext for more draconian sentences or for detaining people unnecessarily". The tweet has since been deleted.
Boris Johnson has released a video saying his "immediate takeaway" from the attack is that serious and violent offenders should not be released early from their sentences.
He says: "It is clear to me that this guy was out, he'd served half his sentence, he was out on automatic early release and I have long said that this system simply isn't working.
"It doesn't make sense for us as a society to be putting people convicted of serious terrorist offences of serious violent offences out on early release and we argue that people should serve the term for which they are sentenced.
"That's my immediate takeaway from this and that's why we are committed to increasing the sentences for serious and violent offenders and why I have argued that when people are sentenced to a certain number of years they should serve every year of that sentence."
More tributes are being paid to victim Jack Merritt, the 25-year-old course coordinator for a prisoners' rehabilitation programme.
After graduating with a bachelor's degree in law from the University of Manchester in 2016, he went on to study at the University of Cambridge where he worked in the criminology department running "Learning Together".
The programme gives students the opportunity to work with inmates as part of their courses and study together in an attempt to reduce re-offending, and involves multiple universities and prisons.
A number of former programme participants, including the killer, had been invited to take part in a conference to mark the programme's fifth anniversary at Fishmongers' Hall in the capital.
A vigil was held in Cambridge on Saturday to mark the incident.
Mr Merritt had appeared on a BBC Radio 4 podcast earlier this year to talk about his work with inmates studying law at Warren Hill prison in Suffolk.
The Metropolitan Police continue to appeal for any witnesses to the attack in Fishmongers Hall to come forward.
Neil Basu said in his statement:
Officers from the Counter Terrorism Command have been working flat out with our security services as you would expect as we continue to try and establish the full circumstances of what happened.At this time, we have found no evidence to suggest anybody else was involved in this attack. However, we are still making extensive enquiries to ensure there were no other people involved. Our investigative priority at this time is to ensure that there is no related outstanding threat to the public.To this end, we have carried out two searches at addresses both in the Staffordshire and Stoke areas. Our officers are being supported with this by officers from Staffordshire and the West Midlands Counter Terrorism Police. I would like to thank them, as well as the local community in those areas, for the support they’ve shown as we carry out these crucial enquiries.The investigation team has also spoken to many of those who were present at Fishmongers’ Hall, but I would appeal to anyone who was there on Friday, or anyone who hasn’t been spoken to, to contact police on 0800 789 321 immediately.
Police are awaiting confirmation from the coroner before identifying the two victims - a man and a woman - who were killed during the attack, although the man has been named online as Jack Merritt.
Two women and a man remain in hospital.
Mr Basu said: "Of course, I am fully aware that the media and social media have named one of those victims. You must understand that I need to wait for formal identification from the Coroner. I will provide an update as soon as I can.
“On behalf of the entire policing family, I would like to offer my heartfelt thoughts and condolences to all those families, both deceased and who still remain in hospital, and everyone affected by this tragedy."
