Social gatherings of more than six people in England will be banned from Monday as Boris Johnson moves to stem the “concerning” rise in cases of Covid-19.
The PM will set out the new rules at a press conference on Wednesday, warning police can hand out fines of £100 to anyone who flouts them.
Cutting the legal limit on gatherings from 30 to six signals growing unease among ministers and government scientists about the possibility of a second wave taking hold in the UK.
The cap will apply both indoors and outdoors – including in private homes, parks, pubs and restaurants.
But 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.
Weddings, funerals and some organised team sports will also be exempt.
The crackdown follows the biggest jump in infections in more than three months on Sunday, when new cases hit almost 3,000.
The UK also reported 30 new coronavirus deaths over a 24-hour period on Tuesday, the highest since July 29.
Health secretary Matt Hancock, who ordered new local lockdown measures for Bolton on Tuesday, has urged people to be vigilant.
He also said young people had been driving much of the latest spike, though ministers feared infection could quickly spread to the vulnerable and elderly without curbs.
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.”
The move follows schools reopening last week.
Chief scientific officer Patrick Vallance and chief medical officer Chris Whitty agreed that urgent action was needed after the jump in cases, Downing Street has said.
As lockdown measures were eased in July, Whitty had cautioned that the country had “probably reached near the limit of what we can do”.
The UK’s coronavirus death toll sits at 41,584 – the fifth highest in the world.