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False claims that a dead union member was given a vote in a narrowly fought selection battle to succeed Unite’s Len McCluskey should be “treated with the contempt they deserve”, a leaked report into the affair has revealed.

In the crucial election for the endorsement of the union’s United Left faction last weekend, veteran shop steward Steve Turner defeated rival Howard Beckett by just three votes.

The result means Turner is now favourite to replace McCluskey at the head of one of Britain’s biggest unions when the election for a new general secretary begins next year.

But supporters of Beckett, who is a vociferous critic of Keir Starmer, challenged the result with claims that irregularities had occurred in the ballot – including one startling allegation that a vote had been cast in the name of a deceased union member.

A report into the conduct of the selection, leaked to HuffPost UK, dismissed suggestions that a Turner-supporting activist who died earlier this year had been given a vote.

“We condemn completely allegations that a vote was provided to and cast by the recently deceased and long-time member of the UL, the well-respected comrade [name removed]. We treat those making such allegations with the contempt they deserve.”

The blog Skwawkbox, a strong supporter of Beckett, had claimed that “at least one deceased member was allowed to vote”.

The report by the independent ballot scrutineer, UK Engage, and United Left chair Jim Kelly, also dismissed claims that 11 Beckett-supporting union members had not been sent ballot papers.

It concluded that all 11 had ballot papers sent to the addresses provided and verified by Progressive United Left Scotland (PULS) – the largest faction of United Left north of the border – prior to the hustings and vote last Saturday.

The report reveals that Beckett asked a string of questions about the conduct of the selection – including how many emails bounced back, and what role was played by the small number of United Left members in Scotland who are not part of PULS but instead make up the rival “United Left Scotland” sub-group. PULS backed Beckett while ULS did not.

Of the 1,089 United Left members eligible to vote across the entire UK and Ireland, 17 ballot emails “bounced” back, but only four people requested a change of address and then voted successfully.

Ten members of United Left Scotland voted. They were “constitutionally” eligible to do so, the report found, and all supplied Unite membership numbers and email addresses.

The report also dismissed other complaints by those it said were unconnected with the election.

“Following the close of the vote several ‘complaints’ and ‘allegations’ have appeared on various on-line social media platforms,” it states.

“These have contained no substance or evidence but have been supportive of the unsuccessful candidate [Beckett]. We have not sought to investigate any of these ‘complaints’ or ‘allegations’, many of which are made by people with no connection with our union or the UL.”

The leaked report contains the full breakdown of the ballot results and shows how nearly two thirds of Beckett’s vote – 237 of his 267 supporters – came from the PULS faction.

A third of Turner’s 370 votes came from London, where he started his union career as a bus conductor 38 years ago.

But he beat his rival in every region other than the East Midlands. In the West Midlands, where Beckett was acting regional director in 2018, Turner narrowly won by 32 votes to 28.

It remains unclear whether Beckett intends to run for the general secretary job, despite his defeat.

Turner, a former Militant member who was backed by the Communist Party, is expected to face a challenge from Gerard Coyne, the centre-right candidate who was narrowly beaten by McCluskey in 2018.