Former campaign director Patrick Heneghan admitted to diverting election funds towards constituencies of mostly right wing, Corbyn-hating Labour MPs.
He also confirmed approving election campaign materials that refused to acknowledge Corbyn for those MPs.
Heneghan is named in a leaked Labour Party report that appeared to show a cabal of unelected senior staff and officials conspiring to undermine Corbyn.
Records of WhatsApp conversations between him and other senior officials show detailed discussions of plans to undermine Corbyn and his supporters inside the party.
They reveal Heneghan’s disbelief at polls that showed Labour was on course to do well, and his deep disappointment at the eventual result. In the event, Labour did much better than expected, denying the Tories an overall majority.
The records also show Heneghan directing sexist abuse at left wing party staff. And he claimed to have told Channel 4 journalist Michael Crick that Corbyn ally Diane Abbott had been spotted crying in the toilets.
In his defence, Heneghan tweeted recently that he had not “seen” Abbott himself, and that he had not “spoken” to Crick.
And in a blog post published last week he responded that he and others had celebrated the election of right wing MPs.
But mostly the post was about taking credit for the 2017 election result. He claimed that by diverting election funds, he had saved seats he claimed were under threat.
“In the 2017 General Election the professional staff of the Labour Party delivered an against the odds performance,” he said.
“By 2019 those staff had largely gone. Instead the pure believers had full control and were able to run the campaign they wanted and electoral oblivion awaited.”
It comes as one opinion poll on Sunday showed Labour with equal support to the Tory government.
It was held up as vindication of current party leader Keir Starmer’s strategy of offering “constructive” opposition to the Tories.
Yet while repeated scandals and failures are surely to blame for the fall in the Tories’ support, Labour has done nothing to harness or shape the reaction against them.
In 2017 Labour’s successful campaign centred around its insurgent feel, involving mass protest-style rallies.
These were absent from Labour’s 2019 campaign, in which Corbyn’s leadership attempted a more conventional, professional approach closer to what the right wanted in 2017.
Far from defeating the Tories, the focus on challenging them in elections rather than through resistance helped them cling on to power.