Labour poured resources into fighting Luciana Berger's bid to be MP for Finchley and Golders Green - but did not prioritise defending Ruth Smeeth's seat, it has been revealed.
In what The Sunday Times called "vindictive internal politics", it revealed Jeremy Corbyn's aides, Seumas Milne and Karie Murphy drew up a list of 86 constituencies to focus resources on.
The list included the seat where Ms Berger was vying to be elected as a Lib Dem, after quitting Labour over antisemitic bullying and abuse, despite the fact most polls for the constiteuncy, including one for the JC, were correctly forecasting Labour would come third behind Ms Berger and Conservative Mike Freer.
Mr Freer won with an 6,562-majority over Ms Berger, triple the amount by which he beat Labour in 2017.
But the list did not include Stoke-on-Trent North, where Ms Smeeth, the parliamentary chair of the Jewish Labour Movement, lost her re-election bid to the Tories by 6,286 votes.
She told the paper: "This dossier just further confirms the incompetence at the highest levels of the Labour Party — not only have they failed to recognise the challenges that we face in terms of leadership, racism in the party and our Brexit policy, they also had no idea how to run the campaign.
"Good colleagues lost by hundreds of votes because seemingly no one in head office was prepared to look at data — they should be ashamed of themselves.”
Other critics of Mr Corbyn, such as Mary Greagh and Melanie Onn, were not on the list of priorities and went on to lose their seats.
On polling day, Ms Berger hit out at her old party after an email went out in Mr Corbyn's name urging London Labour members to campaign in Finchley and Golders Green and Chipping Barnet.
She mockingly asked if the Labour leader was "trolling" her.
She tweeted: "Given you were too busy (for 11 months) to talk to me about your support for an antisemitic mural, how about coming here yourself and we can chat about anti-Jewish hatred in Labour?"
The source who leaked the target list to the Sunday Times told the paper: "We need to know that Corbyn’s successors won’t repeat past mistakes and prioritise winning stupid ideological battles over winning power."
A party insider said campaigners could work "around" the target list, sending resources elsewhere if necessary.
Labour has been contacted for comment.
