It was the political equivalent of running into a burning building with a can of petrol and liberally chucking the fuel over anything you could find.

What Jeremy Corbyn did last Thursday morning almost defied belief.

Mr Corbyn came to the launch of his party's report into antisemitism, conducted by Shami Chakrabarti, after the worst week of his political career.

And he left the press conference at Savoy Place, in central London, in an even more dire position than he entered it. Given the events of the last few weeks, you might ask how things could get any worse for Mr Corbyn?

But there it was, played out in front of our eyes: a Jewish Labour MP challenged until she fled the room, upset at the baseless accusation that she had colluded with a national newspaper.

And at the head of it all, the leader himself, appearing to compare the democratic state of Israel to terrorists.

In the room it sounded as though he made a direct likeness to "Islamic State" - Daesh. It was not a careless throw-away remark - he had written it in advance and included it in his prepared speech. That text suggested he had said "Islamic states" and later clarifications from his spokesman made clear that the intention was to liken Israel to, among others, Hizbollah.

Jewish Labour activists grimaced as the recommendations of the report were not only overshadowed, but blown away.

Ms Chakrabarti admitted it was "not a report that will keep you up late". At barely 30 pages long she was right, but what happened later will give many people sleepless nights.

Mr Corbyn's lack of action as Ruth Smeeth ran from the room prompted one Labour MP to later describe the leader as "a f---ing disgrace". Ms Chakrabarti must rue getting involved.

Even as Mr Corbyn and Ms Chakrabarti left, Marc Wadsworth, the activist who had challenged Ms Smeeth, set about challenging Luke Akehurst, a pro-Israel party member. Then Mr Wadsworth cornered a Daily Telegraph reporter until the chairman of the Commons' press gallery intervened to restore calm.

Mr Corbyn had pleaded with his colleagues to set the "gold standard" for anti-racism in politics. How hollow his words sounded as chaos erupted around him. We may never know how the hard-left pro-Corbyn activists came to be at the launch. Were they invited? By the party, or by the leader's office? How else would they have known the time and location?

Outside the Westminster bubble such details are irrelevant. Labour stands on the edge of a precipice. Its relationship with British Jews is so deeply damaged that it may now be irreparable. Mr Corbyn smiled as he said he was enduring "torrid days", before adding that his ambition for a "kinder, gentler politics" was "still a work in progress". On last week's evidence, such hopes are pure fantasy, both for him and for all of us.

This article has been amended to update the text