The Metropolitan Police Commissioner has warned coronavirus rule-breakers they are "increasingly likely" to face fines as forces move "more quickly" to enforce lockdown restrictions.

Britain's most senior police officer, Dame Cressida Dick, said it is "preposterous" that anyone could be unaware of the need to follow the stringent measures designed to curb Covid-19 cases.

Writing in The Times, she said: "It is preposterous to me that anyone could be unaware of our duty to do all we can to stop the spread of the virus.

"We have been clear that those who breach Covid-19 legislation are increasingly likely to face fines."

However, her comments came as law enforcement sources told the Guardian that police officers would not enforce mask-wearing in supermarkets - despite a Government crackdown on compliance.

Supermarket chain Morrisons said on Monday that customers who refuse to wear a mask without a medical exemption will be told to leave stores, while Sainsbury's also said its security staff would "challenge" shoppers who were not wearing masks or entering stores in groups.

Meanwhile, ministers are reported to be mulling over introducing tougher measures in England, with the wearing of face masks outdoors and banning exercise with people not in their household bubble said to be under consideration.

Tory former health minister Steve Brine led calls for an end to non-essential takeaway sales, including coffee, telling BBC Two's Newsnight: "There are so many things that we are doing, which are allowed in the rules ... but I just don't think they are wise right now."

Health Secretary Matt Hancock warned on Monday that the NHS is under "very significant pressure" and told the public to reduce all social contact that is "not absolutely strictly necessary" in a bid to cut cases.

His warning came as NHS England data showed there were 32,070 Covid-19 patients in English hospitals as of 8am on Monday. The figure is up 20% compared with last week, and up 81% since Christmas Day.

A further 529 people died within 28 days of testing positive for coronavirus as of Monday, taking the UK total to 81,960 - though separate figures show there have now been 97,000 deaths involving Covid-19 in the UK.

Mr Hancock told a Downing Street press conference: "The NHS, more than ever before, needs everybody to be doing something right now - and that something is to follow the rules.

"I know there has been speculation about more restrictions, and we don't rule out taking further action if it is needed, but it is your actions now that can make a difference.

"Stay at home, and please reduce all social contact that is not absolutely strictly necessary. That's what is needed: act like you have the virus."

He said vaccination is the "fastest route to safely lifting restrictions" and the Government is on track to vaccinate the 15 million people most at risk by the middle of February.

Almost 2.3 million people in the UK have been given a first dose of a coronavirus vaccine, according to new figures, while 388,677 second doses have also been given.