However, he sidestepped questions about whether he would resign if it was in the interests of the country or his party, insisting he was focused on fighting the pandemic.

“That is what the Government is engaged in doing now. That is what I am focused on. I think that is what people would want me to be focused on right now,” he said during a visit to a vaccination centre in Hillingdon.

One former Cabinet minister derided his response as a “s*** performance”, but said that while Mr Johnson was “in deep s***” with the party at present, he has “spent most of his life in deep s***” and is well practised at fighting back. 

“Either his love life has been hanging by a thread, or his political life when he was fired by Michael Howard, or his journalistic life when he lied to Conrad Black. 

“He thrives on anarchy, so just because his premiership is hanging by a thread, doesn’t mean it won’t hang for quite a long time,” the MP said.

A year – at most – to sort himself out

Party grandees including Sir Charles Walker insisted it would be “completely self-indulgent” to spark a leadership contest, but added Mr Johnson had 12 months at most to make a difference.

“The Prime Minister has got weeks, months, a year to sort himself out,” he told Times Radio.

Tory MPs elected in 2019 in so-called Red Wall seats across the North and Midlands also cautioned on Friday night that Mr Johnson was in a “very dangerous situation”. 

One said the major revolt over Covid-19 passports on Tuesday night, which was the biggest rebellion of Mr Johnson’s premiership, coupled with the dismal by-election result showed that both MPs and the public were trying to “send him a message”.

The MP continued: “We have to see some central changes, firstly in No 10, and secondly in the way the MPs are managed by the whips and the [liaison role of] PPSes [parliamentary private secretaries].

“I think he’s got one last chance to get that sorted by mid-February next year, otherwise you’re into local election season and after that point I don’t know if you can come back.”

Other narratives were adduced for the defeat in North Shropshire that lay beyond the immediate troubles engulfing Mr Johnson.

Other factors at play for poor Tory performance

John Redwood, a former Cabinet minister, said that high taxes and poor support for Britain’s farmers were to blame for voters turning their backs on the party. 

He also complained that BBC Radio 4’s Today programme cancelled a plan for him to appear when it heard his views on the by-election defeat, implying that journalists there may be rejecting theories that do not match their pre-conceived notions.

Of the two dozen Tory MPs The Telegraph spoke to on Friday, some insisted the by-election result was to be expected at this mid-term juncture in the electoral cycle, arguing it is common for voters to exercise a protest vote then return to the fold at the next general election.

“It will be regarded as really serious [to start with], but [later] colleagues will get stuck into Christmas. I genuinely think this is standard Lib Dem by-election territory,” said one long-standing MP.

Another warned that the period of “crisis may not be over” for Mr Johnson, however, as he could yet face escalating rows over alleged rule-breaking parties in Downing Street, which could “run into Christmas”. 

Simon Case, the Cabinet Secretary, stepped down on Friday night from leading an internal probe on the issue after he was found to have attended a quiz night in his office, billed as a “Christmas Party!” on the digital invitation, while household mixing was banned.

A Cabinet Office spokesman said he “played no part in the event” but had walked through the office and spoke briefly to staff. 

In the past, the whips could breathe a sigh of relief once the Commons had risen for recess and MPs had headed home. Now communication via WhatsApp means plotting and conspiring can continue outside the tearoom and bars of Parliament.

One government source said that while MPs tended to cool off after leaving Westminster for a break, at Christmas time they were likely to be surrounded by relatives who would give them unvarnished views of the PM’s performance. The insider predicted the mood would be worse when the House returns in January.