An increase in coronavirus cases in England has led Prime Minister Boris Johnson to announce a ban on social gatherings of more than six people as of Monday.
The ban will apply to indoor and outdoor gatherings, including private homes, parks, pubs and restaurants.
Offenders will be fined £100, which will double for each repeat offence to a maximum of £3,200.
"We need to act now to stop the virus spreading," Mr Johnson is expected to announce at Downing Street.
"So we are simplifying and strengthening the rules on social contact, making them easier to understand and for the police to enforce."
Exemptions are expected to apply to households of more than six, schools and workplaces.
UK government medical chiefs have warned that the public is too relaxed.
The number of daily positive cases has risen to almost 3,000. On Tuesday there were 2,460 confirmed cases.
It followed 2,948 on Monday and 2,988 on Sunday, which was the largest daily figure since May.
More than 41,500 people are confirmed to died of Covid-19 in Britain, the worst toll in Europe.
The death rate has fallen to its lowest level since mid-March but as in other parts of Europe, cases are increasing.
Mr Johnson's office said medical and scientific advisers agreed that "urgent action is needed", while police had also asked for the rules to be simplified.
"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," he said.
Earlier on Tuesday, the government imposed tougher restrictions on Bolton in north-west England after a "very significant rise" in coronavirus cases.
Health Secretary Matt Hancock said contact tracing data had shown this was "partly due to socialising by people in their 20s and 30s".
After identifying some pubs as hotspots, he announced curbs on hospitality venues, including reduced opening hours, and a ban on locals socialising with people outside their household.
The latest local restrictions come as the government tries to get the economy moving again after months of lockdown imposed in late March.
It has encouraged people to return to work and use a government-subsidised restaurant scheme to boost revenues for those hit hard by the shutdown.
Critics say such measures have only exacerbated infection rates as young people in particular head out to pubs with scant regard for social distancing.
Mr Hancock warned that although younger people were less likely to develop serious forms of Covid-19, they could easily pass it to those more vulnerable, particularly the elderly.
