Boris Johnson has announced the scrapping of all UK travel corridors to "protect against the risk of as yet unidentified new strains" of Covid.

The emergency measure came as the global death toll for coronavirus passed the grim milestone of two million.

It means anyone flying into the country from overseas will only be allowed in if they have proof of a negative test from the previous 72 hours and will then have to isolate for 10 days or for five days if they then test negative again.

The Prime Minister said the policy would come into force from 4am on Monday and apply across the UK. It will last for at least a month.

“It’s precisely because we have the hope of that vaccine and the risk of new strains coming from overseas that we must take additional steps now to stop those strains from entering the country,” declared Mr Johnson at a Downing St press conference.

“Yesterday, we announced that we’re banning flights from South America and Portugal and to protect us against the risk from as-yet-unidentified strains we will also temporarily close all travel corridors from 0400 on Monday.”

The move will be supported by increased enforcement, both at the border and across the UK, with Border Force increasing the number of spot checks on passengers that have entered the country. Anyone flouting the rules faces a £500 fine for any breach.

Sir Keir Starmer welcomed the decision but criticised the UK Government for being slow to act.

“Many people will say: ‘Why on earth didn’t this happen before?’ Many countries have taken this step before we did. Right step, but slow again,” declared the Labour leader.

His party colleague Yvette Cooper, who chairs the Commons Home Affairs Committee, also decried the continuing delays for bringing in tests for travellers to the UK.

Noting how the new ban did not come in until Monday morning, she said: “Due to delays in publishing the Government guidance on pre-travel testing, people can still travel home to the UK from Brazil or Portugal or South Africa this weekend without getting a test.”

Ms Cooper also urged the Government to emulate other countries by introducing testing on arrival, saying: “That could potentially provide an additional check and safeguard before people leave the airport on public transport.”

Tim Alderslade, Chief Executive of trade body Airlines UK, said travel corridors were a “lifeline” for the travel industry when they were introduced in summer 2020 but acknowledged that “things change”.

The travel corridors have been in place since last July for countries and territories where critical analysis suggests the risk of Covid-19 can be mitigated.

However, the Department for Transport said the level of risk associated with the emergence of new variants globally had now increased, requiring “more stringent measures to block all potential avenues through which new strains of the virus could enter the UK while we consider how best to respond”.

Grant Shapps, the UK Government Transport Secretary, said: “We are operating in a completely new environment in our fight against Covid-19 with several worrying new strains of the virus emerging across the globe.

“Now more than ever, as we make strides vaccinating people up and down the country, we need to take advantage of all measures available to us and these robust emergency precautions will help us protect the nation to ensure we continue to make progress.”

At the press conference, the PM appealed to people to abide by the stay-at-home restriction, stressing how because of the “extraordinary pressures” on the NHS – there are now more than 37,000 Covid patients in UK hospitals - this was “not the time for the slightest relaxation of our national resolve”.

As of Friday across the UK:

*a further 1,280 people died, bringing the total to 87,295;

*there were an additional 55,761 lab-confirmed cases, meaning more than 3.3 million people had had the virus and

*the number of people who have received a first dose of a Covid-19 vaccine was 3,234,946 as of January 14, including 224,840 in Scotland; the UK number showed a rise of 316,694 on the day before.

Professor Chris Whitty, England’s Chief Medical Officer, said it was hoped the peak of infections in London and south-east England “already has happened” but would happen later elsewhere.

He suggested the peak of people entering hospital would be in the next week to 10 days for most places while the peak in deaths “I fear, is in the future”.

Prof Whitty repeated it was “very likely” the situation would improve by the spring but cautioned that it would not be completely back to how it was before the pandemic.

He explained: “We’re not going to move from a sudden lockdown situation to nothing. It will have to be walking backwards by degrees, testing what works, and then if that works going the next step.”

Mr Johnson said once 15 million of the most vulnerable people in the UK had been vaccinated by mid-February, “we will think about what steps we could take to lift the restrictions” but he stressed it would depend on what was happening with the virus.

“What we can’t have is any false sense of security so that we, as it were, lift the restrictions altogether and then the disease really runs riot in the younger generations.”

The PM explained that around one third of Covid patients admitted to hospital were under 65 while a quarter were under 55.

“So, it can affect and does affect huge numbers of younger people as well, often very badly, and the risk is that those numbers would be greatly inflated if we let go too soon in circumstances where the disease was really rampant.

“That is not to say that I don’t want to try to get to relaxations as soon as we reasonably can but there are a lot of things that have to go right,” he insisted.

Mr Johnson was keen to remind people to wash their hands thoroughly, saying the virus was not just caught in a supermarket queue but on surfaces.

Sir Patrick Valance, the UK Government’s Chief Scientific Adviser, told the Downing Street briefing the current lockdown had led to a “suppressed peak,” that would “boil over for sure” if controls are eased.

“This is not the natural peak that’s going to come down on its own, it’s coming down because of the measures that are in place.

“Take the lid off now and it’s going to boil over for sure and we’re going to end up with a big problem.”

He stressed: “That’s a lesson about making sure it’s all cooled down enough before you get to that position.”

Sir Patrick also said he expected vaccines would reduce transmission but that “we shouldn’t go mad” as jabs were rolled out.

He warned it would still be the case that people could pass the virus to others.

Asked whether he thought the Brazilian variant causing concern was now in the UK, Sir Patrick said it had “not yet been detected” as far as he was aware.

But he stressed that the situation was being monitored as the variant “could of course come from any place around the world.”