England’s chief medical officer has warned the Indian variant will over time come to “dominate” coronavirus cases in the UK.

Mr Johnson said the UK’s surveillance data is now so advanced that it would see well ahead of time if the NHS was likely to come under unsustainable pressure.

“That gives us the confidence to continue moving forwards for now,” he said.

The army will be deployed on the streets of Blackburn and Bolton to hand out tests to help the surge testing efforts, Mr Johnson said.

There will also be an acceleration of the vaccine rollout there, including longer opening hours at vaccination centres.

“If you’re seeing loved ones, think really carefully about the risk to them, especially if they haven’t had that second dose or if it hasn’t yet had time to take full effect,” the prime minister said.

He added: “I want us to trust people to be responsible, and to do the right thing. That’s the way to live with this virus while protecting the NHS and restoring our freedoms.

“It’s very clear now we’re going to have to live with this new variant of the virus for some time so let’s work together, and let’s exercise caution and common sense.”

Mr Johnson warned that the Indian coronavirus variant could “pose a serious disruption” to plans to ease restrictions and “could make it more difficult” to end them as hoped in June.

The prime minister said: “I do not believe that we need, on the present evidence, to delay our road map and we will proceed with our plan to move to step three in England from Monday.

“But I have to level with you that this new variant could pose a serious disruption to our progress and could make it more difficult to move to step four in June.”

He added that if the Indian variant proves to be “significantly more transmissible” than other strains “we’re likely to face some hard choices”.

But he said there is “no evidence to suggest that our vaccines will be less effective in protecting people against severe illness and hospitalisation”.

Over-50s will be given their second vaccination after eight weeks instead of 12 as alarm grows over the Indian Covid-19 variant, Boris Johnson has announced.

Boris Johnson is now holding a coronavirus press conference from Downing Street. He is joined by England’s chief medical officer, Professor Chris Whitty.

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Glasgow and Moray will remain in Level 3 as the rest of Scotland moves to Level 2, Nicola Sturgeon has announced.

Initially, both areas will remain at Level 3 for a week, with a further decision made at the end of next week.

The situation in Glasgow, the first minister said, is causing even more concern than Moray, with initial research suggesting the outbreak could be being driven by the Indian variant of the virus.

Boris Johnson’s press conference this evening has been delayed until 5.30pm.

Mainland China has reported 12 new Covid-19 cases, including its first local transmissions in more than three weeks, national and regional authorities said.

Four of the cases were local infections in the eastern province of Anhui, all linked to the same case, surnamed Li. State media reported mass testing being carried out in two cities in the province, Luan and Hefei.

Two of the Anhui cases were reported by the National Health Commission on Friday, having been logged on Thursday.

They were the first local transmissions since 20 April, when China recorded two in the southwestern province of Yunnan, where a city on the border with Myanmar reported a new cluster in late March.