Boris Johnson will announce the decision on the 21 June easing of restrictions at a press conference at 6pm on Monday evening, Downing Street has confirmed.
The prime minister will be joined by England’s chief medical officer Professor Chris Whitty and the government’s chief scientific adviser Sir Patrick Vallance.
Health secretary Matt Hancock is expected to give his own briefing at 9pm on Monday.
According to reports, the government has decided to delay the lifting of all remaining coronavirus restrictions in England beyond 21 June.
The date had been earmarked for an end to all COVID-19 restrictions, but a steep rise in cases, caused by the spread of the Delta variant, first identified in India, has led to the delay.
The BBC reported that ministers intend to keep the current rules in place for another four weeks after 21 June, up until 19 July.
The government had intended to remove all legal limits on social contact in England from next week, but the UK recorded 8,125 new daily cases on Friday – the highest tally since February.
Cases of the Delta variant more than tripled last week.
On Sunday, 7,490 cases were reported in the latest 24-hour period.
The removal of restrictions would mean no rules on how many people you could invite into your home, while pubs, restaurants and cinemas would no longer need capacity limits.
Johnson is expected to face a backlash from many Conservative MPs over the planned delay, which will have to be voted on in the House of Commons.
Former minister Mark Harper, chairman of the COVID Recovery Group (CRG) of Tory MPs, said any postponement would be a “political choice”.
He warned that if the unlocking did not go ahead as planned, restrictions could carry on through the autumn and into the winter as other respiratory infections picked up.
But scientists have been warning for weeks that the unlocking should be delayed in the face of rising cases.
Junior health minister Edward Argar said that if the easing were to be delayed for a month, another 10 million second coronavirus vaccine doses would go into arms in this time.
“Were there to be a delay, were that to be what the prime minister announces, we will see what he says and he will make a judgment if he were to delay it on how long by,” he told BBC Breakfast on Monday.
Watch: Boris Johnson faces Tory backlash over lockdown lifting delay