The UK government lifted pandemic restrictions in England on Monday, scrapping all social distancing in a step condemned by scientists and opposition parties.

Starting midnight on Sunday, nightclubs were able to reopen and other indoor venues allowed to run at full capacity, while legal mandates covering the wearing of masks and working from home were scrapped.

Prime Minister Boris Johnson, who is self-isolating after his health minister was infected, urged the public to remain prudent and get vaccinated.

He defended the reopening, dubbed "freedom day," despite scientists' grave misgivings after daily infection rates in Britain topped 50,000, behind only Indonesia and Brazil.

"If we don't do it now, then we'll be opening up in the autumn, the winter months, when the virus has the advantage of the cold weather," the prime minister said in a video message.

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This week's start of summer school holidays offered a "precious firebreak," he said.

"If we don't do it now, we've got to ask ourselves, when will we ever do it? So this is the right moment, but we've got to do it cautiously."

Jonathan Ashworth, the opposition Labour Party's health spokesman, said the government was being "reckless," especially the scrapping of wearing masks, echoing experts who say the reopening endangers global health.

After the success of the vaccination program, which has now offered at least one dose to every adult in Britain, the government says any risks to hospital care are manageable.

Due to the highly contagious Delta variant, more than 54,000 new infections were confirmed on Saturday, marking the highest daily total since January.

In consideration of the deadly variant, Professor Neil Ferguson from Imperial College London warned that Britain was on course for 100,000 cases a day.

However, medics warned even if Britain is suffering far fewer deaths than in previous waves, such a caseload would still put severe pressure on the National Health Service (NHS) and risks seeding new variants.

Officials and experts in UK are looking nervously at Israel and the Netherlands, both of which opened up society after vaccinating most of the population. Both countries have recently reimposed some restrictions after new infection surges.

The government's stated approach of lifting controls now before any winter surge of respiratory disease is marked by "moral emptiness and epidemiological stupidity," said University of Bristol public health expert Gabriel Scally.

(With input from AFP, AP)