Labour’s membership surged to more than 580,000 after its general election defeat, which the party’s official report has blamed on Brexit while largely absolving Jeremy Corbyn.
The post-mortem examination circulated to the party’s ruling National Executive Committee (NEC) found it would be “unrealistic” not to say its policy to hold a fresh referendum played a “decisive” role.
Radicalism was largely ruled out as being at fault in the report by election co-ordinators Andrew Gwynne and Ian Lavery, but they did blame a glut of policies for confusing the public.
While the MPs accepted there were “negative views” of the outgoing leader, there was little blame laid at any of his actions.
A senior Labour source said: “The Labour Party was already by far the biggest party in Britain. It is now even bigger – as big as it has ever been.”
The members will vote along with other supporters for Mr Corbyn’s successor, who will be tasked with restoring the party from its gravest general election defeat since 1935.
The swelling in support after the loss could signal a blow for shadow business secretary Rebecca Long-Bailey, who is closely aligned with the current leadership.
Labour entered the election with a stance of holding another EU referendum on the options of Remain and a “credible” departure deal.
The official report contrasted this policy with the “endlessly-repeated clarity” of the Tories’ “misleading promise to ‘get Brexit done’”.
This allowed Labour to be “unfairly painted” as part of an “obstructive establishment thwarting the people’s will”, it continued.
Key seat targeting in the campaign was also blamed in the report, which shielded the role of the party’s radical manifesto saying its 2017 pledges secured a massive vote increase despite being attacked with “comparable venom”.
“It is unlikely that radicalism was in itself the problem in a country looking for change,” the document said, but pointed towards the scale of pledges seeming “implausible” to many voters.
The report concluded that “too many policies… were launched on an almost daily basis” which “confused the public as to our sense of priorities and disorientated activists”.
“There is also little doubt that four years of unrelenting attacks on the character of the party leader, an assault without precedent in modern politics, had a degree of negative impact,” the report said.
The report was interpreted by some as having absolved Mr Corbyn, a position that was rejected by leadership hopeful Lisa Nandy.
“I haven’t seen the report but I think none of us can be exonerated for the worst election defeat since 1935,” the Wigan MP told LBC.
She said the Brexit position was a factor, which she accused the leadership of having hit the “sweet spot” where both sides of the divide thought the party was against them.
She also said she was now in a “lovely place” having taken Twitter off her phone in an attempt to connect with the voters and not the “Westminster bubble”.
The focus on the social media “hothouse” has been a major problem for the left, Ms Nandy argued, leading to misguided beliefs over when it is failing or succeeding.
“We should be out there amongst the public if we really want to understand what’s happening,” she said.
Ms Nandy and Sir Keir Starmer have both succeeded in getting onto the final ballot of members and supporters to pick the new leader, who will be announced on April 4.
The remaining contenders, Ms Long-Bailey and Emily Thornberry, are still trying to attract sufficient support from unions and affiliated organisations, but the former seems guaranteed to leap that hurdle.