Jeremy Corbyn may have called for unity after decisively seeing off Owen Smith in the Labour leadership challenge, but his plea fell on deaf ears with Lord Mitchell of Hampstead, who announced this weekend that he has quit the party.

Ham & High: Labour leader Jeremy Corbyn is congratulated after the announcement of his election victory in Liverpool today. Owen Smith, his challenger, is pictured in the background. Picture: Stefan Rousseau/PA WireLabour leader Jeremy Corbyn is congratulated after the announcement of his election victory in Liverpool today. Owen Smith, his challenger, is pictured in the background. Picture: Stefan Rousseau/PA Wire (Image: PA/Press Association Images)

The peer, who is Jewish, told the BBC he feels unable to remain within the party under the continued leadership of Mr Corbyn, who polled more than 61 per cent of the vote.

Lord Mitchell, a businessman, had indicated he would leave if Mr Corbyn was re-elected, and said after the result: “I’m a man of my word.”

He accused Mr Corbyn of being “lukewarm” on anti-semitism, and claimed: “He’s hostile to America, he’s hostile to business and he’s pretty hostile to Israel, and I’m the reverse on all those issues as well.

“But there’s one further point. This is a position as leader of the opposition where effectively you are in a position to become the next Prime Minister of this country.

“You cannot become the Prime Minister of this country unless you appeal to the great population, and in particular, middle England, and I think Jeremy has no leadership qualities whatsoever.”

Lord Mitchell was previously part of a damaging split within the Labour Party as a founding member of the Social Democratic Party (SDP) in the early 1980s.

He said he will not join another party, but intends to sit as a crossbencher in the Lords, claiming that Labour is now “a lost cause”.

He said he would not stay in the party and fight for his vision for the party because: “I think the Momentum people, Corbyn’s pals, have got this party by the throat and they’re never going to let it go - at least not in my lifetime.”

The peer claimed that Mr Corbyn surrounds himself with “a coterie of people who hold violent, violent anti-Israel views and allied with it they are very hostile to Jews so, in my view, they’re pretty bad guys”.

He said: “I’m Jewish and I’m very strongly Jewish and I make no bones about it, and there’s no doubt in my mind that Jeremy himsself is very lukewarm on the subject. He’s never been as vociferous in condemning anti-semitism as he should be, and when he does make a mention of it, he combines it with other forms of racism, so he will never say (anything) specifically as far as anti-semitism is concerned.”

But Mr Corbyn took issue with his views, asking: “Has Lord Mitchell ever spoken to anyone in Momentum?”

And the re-anointed Labour leader said it was unfair for Lord Mitchell to claim it is “very difficult” for Jewish supporters of Israel to remain in the party.

He told the BBC: “It’s unfortunate he would say that, because it’s not a fair comment and I would hope he would reflect on that because clearly there are diverse views within the party on issues in the Middle East, but there is absolute unity in the party (in) opposing any form of anti-semitism, and form of racism in the party. That is very clear.”