The UK reported a daily record 1,564 deaths within 28 days of testing positive with coronavirus on Wednesday, as Boris Johnson warned that intensive care units in some hospitals could soon be overwhelmed.

The prime minister told the liaison committee of MPs there was a “very substantial” risk of the NHS running out of ICU beds and no guarantee that schools would be allowed to reopen after the half term break in mid-February.

But Mr Johnson said the numbers of people testing positive for the virus were falling, indicating that existing restrictions should be given a chance to work before tighter curbs are brought in.

Hospital admissions for Covid-19 patients in England fell slightly from 3,967 on January 6 to 3,894 for January 11 — driven by a marked drop-off in London and the South East, although not elsewhere.

“The lockdown measures we have in place combined with tier 4 measures that we were using are starting to show signs of some effect and we must take account of that too,” Mr Johnson said.

“What we’re seeing today is some early signs of progress in restraining the growth of the virus and some signs of perhaps levelling off in some parts of the country.”

But he told MPs it was too early to signal “any kind of relaxation in the middle of February”.

The number of deaths announced on Wednesday is the highest recorded by the government since the start of the pandemic, although limited coronavirus testing during the first wave last year mean daily totals may have underestimated the true toll.

Meanwhile in Scotland, first minister Nicola Sturgeon introduced new restrictions on “click and collect” retail services and businesses offering takeaway food and drink in an effort to tackle the new variant strains of coronavirus.

The new variant first detected in England late last year now accounted for 60 per cent of new cases in Scotland, Ms Sturgeon told the Scottish parliament.

She said that under statutory guidance to take effect from Saturday, only retailers offering essential items such as food, clothes and books would be allowed to operate “click and collect services”. She added that such retailers would have to offer the services outdoors and with staggered appointments.

Ms Sturgeon said takeaway food would now have to be given from a “serving hatch or doorway” rather than indoors, as currently permitted, and a legal ban would be imposed on drinking alcohol in public in most of Scotland.

Downing Street has been discussing a similar tightening of restrictions, including measures such as the closure of nurseries and a ban on click and collect services at non-essential retailers.

Mr Johnson said the trajectory of the pandemic in the coming weeks would depend on the success of the government’s vaccination campaign. But he urged people to “keep their discipline” and said further restrictions could not be ruled out.

Mr Johnson told MPs that he was concerned about a new strain of coronavirus identified in Brazil. He said it was not clear whether or not the new variant was resistant to vaccines.

He also defended the NHS Test and Trace programme, saying it had carried out 56m tests — the highest number of any European country.