The UK has recorded another 46,169 coronavirus cases and 529 deaths.
The latest data takes the total number of fatalities within 28 days of a positive COVID-19 test to 81,960.
There have been 3,118,518 confirmed cases in the UK since the pandemic began - the fifth-highest in the world, according to Johns Hopkins University.
On Sunday, there were 54,940 cases reported and 563 more deaths recorded.
One hospital in Essex has been forced to start managing oxygen supplies because of the number of coronavirus patients needing treatment.
Meanwhile, Boris Johnson has warned that the government "may have to do more" if ministers feel lockdown rules "are not being properly observed".
Health Secretary Matt Hancock has revealed that 2.6 million coronavirus jabs have now been administered to 2.3 million people across the UK.
He also warned that the new variant of coronavirus is "highly contagious and it is putting the NHS under very significant pressure".
At the Downing Street briefing, England's chief medical officer Professor Chris Whitty said "we're probably at the worst point in this pandemic" - and the latest government data shows that 3,098 patients are on ventilation.
Professor Whitty added: "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."