In a competitive field, yesterday was the most surreal - and shameful - day for Labour since Jeremy Corbyn became leader. After a telling delay, Corbyn arrived at the only response that was acceptable to MPs: the suspension of Ken Livingstone. The former mayor of London, who appears incapable of entering a studio without triggering outrage, surpassed himself by claiming Hitler supported Zionism (as if to invalidate the latter). In time-honoured fashion, he then responded to criticism by pouring petrol on the fire. In remarks that caused journalists to question their hearing, Livingstone opined that "a real anti-Semite doesn't just hate the Jews in Israel".

Two hours later, one of Corbyn's greatest allies was finally suspended (the day after Naz Shah MP had been). But the announcement itself added new offence. The email confirming Livingstone's suspension simultaneously revealed that John Mann MP, who had denounced the former mayor as a "Nazi apologist", had been summoned by the chief whip to "discuss his conduct" - as if their behaviour was somehow comparable. Labour sources later told me that Corbyn's office had wanted to go further and suspend Mann - a demand flatly rejected by the whips. Their resistance has revived the desire among some of the leader's allies for a cull in a future reshuffle.

But it was Corbyn's conduct in a BBC interview that truly provoked MPs' fury. "It's not a crisis, there's no crisis," he declared, unwittingly echoing the Sun's headline on Jim Callaghan during the Winter of Discontent ("Crisis? What crisis?"). It was as if Hitlergate had never happened. Corbyn added that "the party membership is the biggest it has been in my lifetime" (it was actually higher in 1997) and that "much of this criticism that you are saying about a crisis in the party actually comes from those who are nervous of the strength of the Labour Party at local level". MPs, he appeared to suggest, were not motivated by a desire to repel Labour's anti-Semitic infection but by fear of the party's left-wing membership.

Livingstone's suspension was "very sad", Corbyn said, but "there is a responsibility to lead the party". The abiding impression was that he had suspended his old comrade with the utmost reluctance - it was the burden of office that had forced him to do so. Finally, Corbyn declared, as he always does on these too-frequent occasions, "we are not tolerating anti-Semitism in any way or indeed any other kind of racism." Labour's leader appears congenitally incapable of condemning Jew-hatred in insolation. The explanation, some MPs say, is that he subscribes to a "hierarchy of racism" under which anti-Semitism is a lesser offence than, say, Islamophobia. In rejecting a systematic focus on the former, Corbyn's critics say he is in denial about the scale and significance of the infestation.

His apathy has intensified the desire of his opponents to remove him before the year is out. "The soft left moved massively today," one MP told me in reference to Labour's internal swing voters. Another said: "It does two things: it firmly pins responsibility for next week's results on the hard-left antics [Labour is forecast to become the first opposition since 1985 to lose council seats in a non-general election year] and it weakens the willingness of the 'core group' servers to keep mopping up after Corbyn because they are increasingly mortified by the association". But others disagreed: "It's strangely less likely," one said of the prospect of a challenge, "the mood is 'keep giving him the rope'". Another said that Labour MPs, traditionally sentimental towards their leaders, lacked the "constitution" for the struggle. "They can always find an excuse why now isn't the right time," he lamented. Without an agreed candidate, and without even agreement on whether there should be a challenge, Corbyn's opponents fear that "even worse is to come".