A week after Tony Blair’s pro-Remain cry, Jeremy Corbyn rose to deliver a speech on “the road to Brexit”. But it is the road to ruin that Labour MPs believe he is leading them along. The party last night became the first opposition to lose a by-election to the government since 1982. Were the Copeland cataclysm replicated across the country (and Labour traditionally underperforms at general elections), the Conservatives would win a majority of 114.

MPs believe this new nadir is not in spite of Corbyn but because of him. They blame his historic opposition to nuclear power (the seat’s major employer) and personal unpopularity for the Tories’ triumph (with the largest swing to a governing party since 1966). In his speech, Corbyn hailed Labour’s victory against Ukip in the accompanying Stoke by-election (though Paul Nuttall didn’t make it hard for them) and attributed the Copeland defeat to voters feeling “let down by the political establishment”. Yet in the Cumbrian constituency it was not a populist upstart that benefited but Theresa May’s government. Even the Prime Minister’s refusal to save local maternity services (“Babies will die,” warned the opposition) wasn’t enough to spare Labour.

Asked by ITV journalist Chris Ship whether he had “looked in the mirror” and asked “could the problem actually be me?”, Corbyn flatly replied: “No”. He did not sound as if he was lying. “Why not?” pressed Ship. “Thank you for your question,” the leader said.

Corbyn speaks with the confidence of a man who knows that he is, for now, unassailable. In Labour’s internal conflict, it is not last night’s result that counts but last year’s leadership election. Corbyn emerged strengthened from that contest and MPs fear a similar outcome in the event of a new contest. Though activists express increasing anxiety about the party’s fortunes, most remain loyal to the leader they re-elected last summer. “We are a campaigning party, we campaign for social justice in this country,” Corbyn emphasised. Many voted for him believing, after the Tories’ surprise majority, that the 2020 election had been lost in advance. From this perspective, opposition is not the means to an end (government) but an end in itself.

The bulk of Corbyn’s speech was a defence of the party’s decision to accept Brexit. In the post-referendum climate, Labour is being squeezed by the pro-Remain Lib Dems and the pro-Leave Tories (who have benefited from Ukip defectors). Though the party has championed amendments, such as one guaranteeing EU nationals’ rights, its commitment to vote for Article 50 regardless meant its efforts have struggled to acquire momentum. “No deal is a bad deal,” Corbyn declared of May’s threat to depart without an agreement. But that the Prime Minister can even float this possibility is a mark of Labour’s weakness.

A day may yet come when Corbyn faces a palace coup or reaches for the pearl-handled revolver. But Copeland is proof that his job is far safer than those of many of his MPs.