The police will enforce the local lockdown in Leicester - and Matt Hancock has threatened to change the law in order to enforce the rules.
From today non-essential shops in Leicester must close all over again and schools will shut their doors from Thursday.
As the rest of England prepares to ease restrictions from July 4, the reopening of pubs and hairdressers in the city has been cancelled because of rising cases.
The Health Secretary has said Leicester's seven-day infection rate is 135 cases per 100,000, which is three times higher than the next highest city.
And today he told Sky News: "We will be bringing forward a legal change very shortly, in the next couple of days, because some of the measures that we've unfortunately had to take in Leicester will require legal underpinning."
Mr Hancock said "in some cases" the lockdown would be enforced by the police, while legal changes would be made so non-essential retail is no longer open.
When pressed on how people would be stopped from travelling outside the city, he said: "We're recommending against all but essential travel both to and from and within Leicester, and as we saw during the peak, the vast majority of people will abide by these rules.
"Of course we will take further action including putting in place laws if that is necessary but I very much hope it won't be."
Mr Hancock said a range of targeted interventions over the last week or so - including working with factories that saw a spike in cases - had not managed to stem the outbreak.
He told BBC Breakfast: "We have been monitoring it incredibly closely, we have put in extra testing units, some of the schools in Leicester were closed already.
"We also went into some of the factories and workplaces where there was an outbreak and we put in place measures.
"These sorts of much more targeted measures have worked in other outbreaks.
"So we've been taking this highly localised approach but unfortunately that targeted action wasn't working in Leicester and that's why we have taken this much broader measure."
There had been widespread confusion over exactly which towns and villages in Leicestershire are included in the lockdown.
Leicester City Council tweeted on Tuesday morning: "We haven't got all the information we need yet about the #LeicesterLockdown."
But it published a list of affected areas, including Braunstone Town (including Fosse Park), Glenfield, Glen Parva, Leicester Forest East (east of the M1) and Thorpe Astley.
It also said Birstall, Thurmaston and all areas of Oadby and Wigston were included.
Earlier, Mr Hancock did not rule out forcing people to stop travelling outside of Leicester but said he hoped people would heed the new advice.
He said: "On travel, we are recommending against travel unless it is essential but we are not putting that in place in law at this stage.
"Of course we will if we have to."
A statement from Leicestershire Police said: "This is a dynamic situation and we will adjust accordingly providing proportionate policing under the relevant legislation to help keep people safe in Leicester, Leicestershire and Rutland.
"Our approach has always been clear that we will use the four Es - engage, explain, encourage and enforce where necessary."
Mr Hancock said work was still being done to understand why Leicester had been so badly affected by the outbreak, adding that possible causes such as poverty, higher ethnic diversity, language difficulties and higher-density housing were "familiar" to him.
He told the BBC: "We are still doing the work to understand exactly why the outbreak has been so bad in Leicester.
"But lots of the reasons that you mentioned just then are familiar to me and people will find them intuitive."
There has been a relatively high number of cases among children in Leicester, but Mr Hancock stressed that youngsters were at low risk of serious illness from coronavirus.
Defending the decisions on schools reopening, he said: "Where the prevalence is now very low in large swathes in the rest of the country, essentially, then reopening of the schools is safe.
"But when the disease starts to spread fast as it is doing in Leicester, then we do have to close the schools but it's not for the protection of the children because they're safe at school, it's to slow the spread."
Mr Hancock told BBC Radio 4's Today programme that the fact the disease was under control in the rest of the country meant schools could reopen elsewhere in England, including in September.
"In the vast majority of the country, that's why we are able to to reopen schools, precisely because of the action that we take and we know what works to get this virus under control.
"And so that's why it is OK to open schools in September, because it's under control, and the whole strategy, the whole plan is to try to lift the national measures and have more targeted measures in the places where there's outbreaks."
Former health secretary Jeremy Hunt said the Leicester lockdown was a "necessary puncturing of the elation that had been building up throughout the country" in the run-up to the easing of restrictions on July 4.
He also told the Today programme the easing of restrictions would be a "stop, go" process until there is a vaccine.
Meanwhile, shadow chancellor Anneliese Dodds said having a properly functioning contact tracing system in place was the only way to prevent additional lockdowns.
She said: "The more fine-grained and localised we can make the lockdowns, the better, but that will only happen when test, trace and isolate is running in the UK as it is already in other countries."
Elsewhere, Britain's most senior police officer has urged the public to be calm and sensible when pubs reopen in much of England on Saturday.
Metropolitan Police Commissioner Dame Cressida Dick said: "You will see a lot of police officers out on the street.
"There will be a lot more ready should people be out of order, should people get violent. But I'm not predicting that at this stage."
Dame Cressida added: "My message is, if you're coming out on Saturday, be calm, be sensible. Look after yourself, look after your family.
"We are still in a global pandemic which is affecting this country very obviously. People need to be sensible."
Meanwhile, the Prime Minister will use a keynote speech in the West Midlands on Tuesday to say his message is "build, build, build" as the UK comes out of lockdown after the Covid-19 pandemic, and that the Government intends to spend £5 billion "to accelerate infrastructure projects".
