England’s Covid restrictions will be lifted nationally but local lockdowns could be “reimposed” to tackle new variants, Boris Johnson has announced.

Under the roadmap set out by the prime minister on Monday, all rules limiting social contact could end by June 21.

England will not return to the regional system of tiers that was previously in place.

But amid concern new variants of the illness could derail the plan, the prime minister told MPs: “We can’t rule out reimposing restrictions at local and regional level if the science suggests they are necessary to contain or suppress a new variant.”

The roadmap document released by Downing Street added it was important to keep watch for “local outbreaks and variants of concern”.

“Strong measures are in place at the border to mitigate the risk of importing new cases and new variants,” it said.

“Where a dangerous variant of concern is identified and is likely to pose a real risk to the vaccination programme or public health, the government will take a highly precautionary approach, acting fast to address outbreaks.

“The government will also act quickly where an area sees unmanageable virus growth or the NHS is at risk, with local intervention centred on testing, communications and enforcement.”

Johnson’s plan to ease rules will see all pupils in all years in England will go back to the classroom from March 8.

Socialising in parks and public spaces with one other person will also be permitted from that date, to allow people to sit down for a drink or picnic.

Speaking in the Commons, Johnson said: “The threat remains substantial with the numbers in hospital only now beginning to fall below the peak of the first wave in April.

“But we are able to take these steps because of the resolve of the British people and the extraordinary success of our NHS in vaccinating more than 17.5 million people across the UK.”

A further easing of restrictions will take place on March 29, with larger groups allowed to gather in parks and gardens.

From April 12, non-essential retail could reopen and pubs and restaurants might be allowed to serve customers outdoors.

From May 17 household mixing indoors could be allowed, with pubs and restaurants allowed to operate indoor table service.

And in the final phase of the plan, all social contact restrictions could be lifted on June 21.