Boris Johnson has signalled that he will take a cautious approach to easing restrictions in an attempt to make it the last national lockdown to combat the coronavirus pandemic.

The Prime Minister said yesterday the "far more sensible approach" is to reopen "safely and cautiously", starting with schools, to prevent a rapid resurgence of infection rates.

He will likely face opposition from Conservative backbenchers who are eager for him to release the restrictions as soon as the most vulnerable groups receive some immunity from vaccination.

Chief medical officer Professor Chris Whitty warned even a "very small change" with cases so high could cause a rapid resurgence while chief scientific adviser Sir Patrick Vallance warned against "getting too hooked" on specific dates for easing measures.

After disclosing fears the new UK strain could be even more deadly than previously thought, Mr Johnson told the Downing Street press conference Covid-19 will have to be lived with "for a long while to come".

"I also think that the British public and British business would much rather we opened safely and cautiously when it was right to do so rather than opening up again and then being forced to close back down simply because the virus takes off again," he added.

"I think that is a far more sensible approach."

Amid warnings the Brazilian and South African variants may be less effective against vaccines, Mr Johnson did not rule out closing the UK border to foreign travellers.

Prof Whitty said the situation remained "extremely precarious" and that "a very small change and it could start taking off again from an extremely high base".

"If people took this moment and said, 'Right, it is over', it would get back into very deep trouble very fast and the NHS is absolutely at the top of what it can manage," he warned.

"If that happened again, we would be in really, really deep trouble."

The Covid Recovery Group (CRG) of Conservative lockdown-sceptic MPs said ministers "must start easing the restrictions" in March when the top four risk groups should have received some immunity from single jabs.

Sir Patrick countered this call, saying: "The key thing, I think, is to keep watching, measuring and assessing where we are and not getting too hooked up on specific dates, because we don't know at the moment.

"We need to watch, wait, measure and release carefully as we go through it."