Boris Johnson has threatened to intervene and impose the toughest Covid-19 restrictions in Manchester – despite local council leaders’ staunch opposition to the move.

Speaking at a press conference in Downing Street, the prime minister urged Greater Manchester mayor Andy Burnham and others to “reconsider and engage constructively” over tier 3 restrictions. 

The move can see the most stringent measures imposed, with pubs, gyms, casinos and leisure centres potentially in the firing line and people unable to mix with others outside their household. 

Burnham said the city would not accept restrictions without a return of the 80% furlough scheme – which government wants to cut to two thirds of lost wages – and has accused Johnson of treating the north like “a sacrificial lamb”. 

Tier 3 would “sacrifice jobs and businesses” in the region “to try and save them elsewhere”, Burnham said, as he threatened legal action at a town hall press conference on Thursday. 

But Johnson made clear he would “intervene” if hospital admissions continued to refuse, saying intensive care admissions were set to spiral in the coming two weeks to levels not seen since the height of the first wave. 

“On recent trends, in just over two weeks there will be more Covid patients in intensive care than at the peak of the first wave,” he said, “so I urge the mayor to reconsider and engage constructively.

“I cannot stress enough: time is of the essence. Each day that passes before action is taken means more people will go to hospital, more people will end up in intensive care and, tragically, more people will die.

“Of course, if agreement cannot be reached I will need to intervene in order to protect Manchester’s hospitals and save the lives of Manchester’s residents. But our efforts would be so much more effective if we work together.”

On Thursday afternoon, Burnham said he was “fighting back for fairness” and would “stand firm”, arguing that tier 3 would not work and a time-limited national lockdown, recommended by government scientists on September 21, was the only option.

Chief scientific officer Patrick Vallance, who appeared alongside the PM on Friday, appeared to agree. 

He said the “baseline” tier 3 measures on their own would not be enough to get the numbers of infections down.

“Where we are now is a different situation,” he said. “It is crucial that, where the R is above 1 and the numbers are high, we get the R below 1.

“There are a number of ways that it can be done. As the chief medical officer said, tier 3 baseline [measures] on their own, almost certainly, aren’t enough to get the R below 1.”

Meanwhile, on Friday, Lancashire was placed into the highest Covid-19 alert level, tier 3, sparking a blazing row between Downing Street and council leaders. 

Sheffield city region mayor Dan Jarvis also said “constructive” talks had begun with government over the alert level for South Yorkshire.

Johnson said he would resist another national lockdown “if at all possible”, however, despite growing pressure to impose a short England-wide “circuit-breaker”.

“Some have argued that we should introduce a national lockdown instead of targeted local action and I disagree,” he said. 

“Closing businesses in Cornwall where transmission is low will not cut transmission in Manchester.

“So, while I can’t rule anything out, if at all possible, I want to avoid another national lockdown with the damaging health, economic and social effects it would have.”

The UK’s R value, which tracks the reproduction rate of the virus, also rose slightly to between 1.3 and 1.5, having been in the range 1.2 to 1.5 last week.

An R above 1.0 means the pandemic is growing and a value between 1.3 and 1.5 means that on average every ten people infected will infect between 13 and 15 others.