The MI5 director general, Ken McCallum, has acknowledged his frustration at the failure to put on trial two Britons who had been accused of spying for China, in an apparent rebuke to prosecutors who dropped the high-profile case last month.
The domestic spy chief insisted he would “never back off” from confronting threats from Beijing, which he said posed a national security threat “every day”, although the wider UK-China relationship was a matter for the government.
A China-related spy plot was disrupted “in the last week”, he said, though it is understood not to have involved parliament, while the number of individuals under investigation over all state-based threats is up 35% in the last year.
Giving a long-planned annual update, the MI5 chief was asked to comment on a surprise decision by the Crown Prosecution Service to abandon the prosecution of Christopher Cash, a parliamentary researcher, and Christopher Berry last month.
“Of course I am frustrated when opportunities to prosecute national security threatening activity are not followed through for what ever reason,” the spy chief said, though he added that MI5 had been successful in halting the activities the two men had been accused of.
“Clearly when we believe there has been activity threatening UK, national security convictions are great. We work very hard with our police colleagues to make those possible. And so, it’s frustrating when they don’t happen.
“But I would invite everyone to just not miss the fact this was a strong disruption in the interests in UK national security,” McCallum said in a question-and-answer session with journalists that came after he gave a speech.
Cash, who worked for Conservative MPs Tom Tugendhat and Alicia Kearns, and Berry, a teacher and researcher based in China at the time, were accused of spying for Beijing by passing on information from parliament to a Chinese agent known as “Alex” and Cai Qi, a member of the country’s ruling politburo.
The two men denied the charges, and have always asserted their innocence. However, questions have swirled as to why the CPS thought it had enough evidence to charge the men in April 2024, under a Conservative government, but felt they had to drop the case under Labour after a change to the case law.
The case collapsed in the end, the CPS said, because Matthew Collins, a deputy national security adviser, had failed to give evidence on behalf of the government that clearly described China as a current “threat to national security” as required by the 1911 Official Secrets Act under which they were charged.
Asked specifically about whether he thought China did pose the threat level required by the prosecution, McCallum said: “Do Chinese state actors present a UK national security threat? And the answer is, of course, yes they do every day.”
But he said that “the overall balance of UK bilateral foreign policy relationships” was “perfectly legitimately a matter for government” – and added that he was “not going to presume to appoint myself a temporary expert in the running of prosecutions”.
At one point, in his initial speech, the spy chief personalised the agency’s response to the spy row, saying: “I am MI5 born and bred. I will never back off from confronting threats to the UK, wherever they come from.”
Overnight, Downing St published the three witness statements submitted to prosecutors by Collins, whose job it was to represent the government policy in court. They showed that the CPS dropped the case despite being told by Collins that China’s intelligence agencies “harm the interests and security of the UK”.
McCallum described Collins as “a man of high integrity and a professional of considerable quality” and a person who he had known professionally for some years.
Ministers have previously said that the task of writing the witness statements was for Collins without reference to politicians and that the prime minister, Keir Starmer, only saw their contents for the first time on Wednesday morning.
The MI5 chief also said his agency was contending with “a more hostile world” that is “forcing the biggest shifts in MI5’s mission since 9/11”. A total of 19 late-stage terror attack plots, running at a rate of about four a year, had been disrupted since the start of 2020 and he warned that al-Qaida and Islamic State were seeking to revive.
He offered his “deepest sympathies” to the victims of the Manchester synagogue attack, conducted by an individual who had pledged allegiance to IS in a 999 call, describing the terrorist incident as “horrific violence against a community at prayer”.
But despite the signs of established terror groups “becoming more ambitious” the main terror threat in the UK came from “individuals or small groups” often from problematic or troubled individuals who were radicalised online.
“Terrorism breeds in squalid corners of the internet where poisonous ideologies, of whatever sort, meet volatile often chaotic lives,” he said.
The vast majority of other state based threats came from Iran and Russia. MI5 has tracked “more than 20 potentially lethal Iran backed plots” in the past year, McCallum said. Investigators had also disrupted “a steady stream of surveillance plots with hostile intent” from Russia, which often seeks to recruit untrained proxies online.
MI5 also continued to see “a concerning number of minors” in its national security investigations, the spy chief said, with one in five of the 232 terrorism arrests last year were of children under 17.
The agency said it had helped create an Interventions Centre of Expertise, to try and manage threats in cases involving adolescents, staffed with both national security experts and professionals from the wider public sector.
