Lord Mandelson reportedly walked out of an event at Hampstead Synagogue on Sunday night after a row over antisemitism in the Labour Party broke out.

The life peer allegedly said it was “disgraceful” to suggest that Starmer’s Labour Party is still mired by Jew-hate.

The tense interaction unfolded during the 21st annual Isaiah Berlin lecture, which was delivered by Sir Anthony Seldon and was titled ‘Has the job of Prime Minister become impossible?’

Sir Tony Blair’s ‘spin doctor’, Lord Peter Mandelson, was sitting in the front row and journalist and editor of TheArticle, Daniel Johnson was also in the 250-strong audience at the north-west London Shul.

During the question-and-answer session, Johnson posed a question to Sir Anthony. The journalist said: “Antisemitism hasn’t been a factor in British politics really since the 1930s. But it now very much is, and Keir Starmer told us that he’d sorted out this problem in the Labour Party.”

“But it’s very obvious that he has not. So what do you think about that? I mean, he will undoubtedly win the next election. But I think many people in this room will feel very uncomfortable about voting for a party that is still clearly mired…”

According to The Telegraph, before Sir Anthony could answer the question, Lord Mandelson interjected: “Oh that’s disgraceful. It’s disgraceful to say that.”

Johnson responded: “Well, it’s true – look at Rochdale” - a reference to the by-election candidate Azhar Ali, who was suspended from the Labour Party after conspiratorial comments came to light in which he said Israel had allowed October 7 to happen as a pretext to invade Gaza.

Sir Anthony asked Johnson what more Sir Keir Starmer would need to do to “prove to you that he isn’t Jeremy Corbyn and that he’s really got on top of this disease of antisemitism”.

Johnson replied: “Winston Churchill, Harold Wilson, Margaret Thatcher, Tony Blair were all very obviously philo-Semitic people who were strong defenders of Israel. Has Keir Starmer done that?”

Allegedly, Lord Mandelson then shouted: “It’s a nasty smear, a really nasty smear; I’m ashamed of you.”

Some in the audience applauded this interjection.

Johnson responded: “You [the Labour Party] were investigated by the EHRC – no other political party has ever had that before.” The equality watchdog launched an investigation into the Labour Party in 2019 following serious allegations of antisemitism and it found that the Party had acted unlawfully.

The Labour peer quipped: “Do you not have any sense of knowledge or decency, Daniel? What do you think he’s done since that report?”

After the EHRC report, Sir Keir said he would have a “zero-tolerance approach to antisemitism and racism”, and suspended members of the Party over allegations of antisemitism, including former leader Jeremy Corbyn after he claimed that Jew-hatred in the Party had been "exaggerated".

Soon after Johnson suggested that the Labour Party still had an antisemitism issue, Lord Mandelson left the event before the Q&A session had ended.