Social gatherings of more than six people will be illegal in England "for the forseeable future" from Monday as the Government seeks to curb the rise in coronavirus cases.
Prime Minister Boris Johnson will use a press conference on Wednesday to announce the change in the law after the number of daily positive Covid-19 cases in the UK rose to almost 3,000.
The legal limit on social gatherings will be reduced from 30 people to six.
It will apply to gatherings indoors and outdoors – including private homes, as well as parks, pubs and restaurants.
Health Secretary Matt Hancock said he hopes the ban can be reversed by Christmas.
He told BBC Radio 4’s Today programme: “It’s absolutely therefore the foreseeable future. I really hope we can turn this round before Christmas.
“I think that, in a pandemic, Christmas is a long way off."
He also insisted the public should follow the new rules on social distancing despite the government’s willingness to break international law over the EU Withdrawal Agreement.
He told LBC: “Obviously we are determined to deliver Brexit at the end of the transition arrangements with the EU, there has been good work going on, I very much hope and expect that we will get a deal.”
“We are putting the peace process in Northern Ireland first and I think everybody would understand why we have decided to do that.”
Gatherings of more than six people will be allowed where the household or support bubble is larger than six, or where the gathering is for work or education purposes.
Exemptions will also apply for weddings, funerals and organised team sports in a Covid-secure way.
While the restrictions are not as severe as they were from March to June, Mr Hancock refused to rule out a second lockdown, despite assurances by the Prime Minister.
Speaking to LBC, he said: “I wouldn’t make a vow like that.
“You wouldn’t expect me to – I am the Health Secretary in the middle of a pandemic where we are trying to keep the country safe.”
But he added he “hoped” lockdown could be avoided, saying: “The number of cases is largely driven by people socialising.”
ITV News Political Editor Robert Peston explains what he has learned from the latest coronavirus measures from the government
Mr Johnson is expected to tell the press conference: "We need to act now to stop the virus spreading. So we are simplifying and strengthening the rules on social contact - making them easier to understand and for the police to enforce."
"It is absolutely critical that people now abide by these rules and remember the basics – washing your hands, covering your face, keeping space from others, and getting a test if you have symptoms."
His press conference comes just a day after England's Deputy Chief Medical Officer warned the rise in coronavirus cases is of a "great concern".
Professor Jonathan Van-Tam said the recent surge is a "big change" and after the outlook seemed to "relax over summer."
He added if the UK doesn't get its case numbers under control the country could have a "bumpy ride over the next few months."
Mr Van Tam said: "This is a big change, it's now consistent over two days and it is of great concern at this point.
"I think you know we've been able to relax a bit over the summer, the disease levels have really been quite low in the UK through the summer but these latest figures really show us that much as people might like to say 'oh it's gone away', this hasn't gone away," he said.
Mr Van-Tam's warning mirrors a member of the Scientific Advisory Group for Emergencies (SAGE) who on Tuesday told ITV News' Political Editor Robert Peston that case numbers were "increasing exponentially."
Professor John Edmunds warned the R number in England was already above 1 and this could be made worse by schools and universities reopening nationwide.
He said the UK was facing a serious challenge to control the virus over the autumn.
Prof Edmunds added: "The epidemic continues to increase and then we have Christmas. And that is very difficult. What is Christmas?"
"Well it's meeting with your family very close. Restaurants and pubs and stuff like that. And it's all high risk. And it's all indoors. Indoors makes a difference."
He continued: "We've been lucky with the weather - and it's turned".
Downing Street said chief medical officer Professor Chris Whitty, chief scientific adviser Sir Patrick Vallance and the Government had jointly agreed that urgent action was needed after the rise in coronavirus cases.
Some 2,420 lab-confirmed cases of coronavirus were recorded in Britain as of 9am on Tuesday, following the 2,988 reported in the UK on Sunday, which was the largest daily figure since May.
The Government hopes that the change to the law will make it easier for the police to identify and disperse illegal gatherings. Failure to comply could result in a £100 fine, which will double on each repeat offence up to £3,200.
Number 10 said Mr Johnson held a virtual roundtable with police forces last week where officers expressed their desire for rules on social contact to be simplified.