Boris Johnson has refused to rule out a national “circuit breaker” lockdown – but insisted local restrictions “will drive down the virus”.

The prime minister defended his three-tier plan under pressure from Keir Starmer, who is now calling for a short national lockdown to “save lives, fix testing and protect the NHS”.

Johnson described the Labour leader’s shift, announced dramatically on Tuesday night, as an “extraordinary U-turn” and defended his local plan.

At prime minister’s questions, he insisted he wanted to “try to avoid the misery of another national lockdown”.

But, after Starmer quizzed him on briefing from government sources to the Telegraph that there is an 80% of a circuit break in the next two weeks, the PM said: “I rule nothing out.”

Scotland and Northern Ireland have both recently announced circuit breaker lockdowns, with measures including banning pubs from selling alcohol indoors in Scotland, and shutting schools for a fortnight in Northern Ireland.

The Labour leader decided to back a circuit breaker after papers published on Monday night showed that the PM rejected calls from his own Scientific Advisory Group for Emergencies (Sage) to impose a short two-week national shutdown on September 21.

Starmer asked why Johnson had decided to “reject that advice and abandon the science”.

Responding, the prime minister said he has been advised that a “regional approach” to tackling Covid will “bring down the virus” and stressed that Sage had also noted “associated costs in terms of health and wellbeing” and the “economic impacts” of a circuit breaker, which he had to consider when making a decision.

In a later exchange, Starmer said: “I think this measure is wrong and a circuit breaker is in the national interest.

“I’ve read the advice from Sage, and the government has rejected it.”

He went on: “This is my last question, I’m sure the prime minister will have a pre-prepared rant ready as usual.

“But we are at a tipping point – time is running out.

“Maybe he can seize the moment and answer a question.

“This morning the Telegraph quotes senior government sources saying the chances of the prime minister backing a circuit break in the next two weeks are about 80%.

“Is that right?

“And if it is, why doesn’t he do it now, save lives, fix testing, and protect the NHS?”

Johnson replied: “The right honourable gentleman [Starmer] claims to be supporting the government one day and then performs a dramatic U-turn the next.”

He went on: “Everybody can see what he’s doing, Labour have said it themselves – they see this as a ‘good crisis’ for the Labour Party and one they wish to exploit.

“We see this as a national crisis that we are going to turn around.

“And the way we are going to do it – and I rule out nothing in combating the virus – but we are going to do it with the local, the regional approach, that can drive down and will drive down the virus if it is properly implemented.

“That’s what I believe he should be supporting. He said he’d support it on Monday.

“This is our opportunity to keep things going, to keep our kids in school, to keep our businesses going – that is what I think the people of this country want to do.

“This is our opportunity to do that and to suppress the virus where it is surging.”