SCOTTISH Labour’s leadership battle has descended into a civil war that could split the party, after both sides accused the other of rigging the contest.

Yesterday, that fight was played out in public when Ian Murray, the former Shadow Secretary of State for Scotland, raised questions over the number of union affiliates who had registered to vote for left wing candidate Richard Leonard.

In a letter to the party’s Scottish general secretary, Brian Roy, Murray wrote: “I take absolutely no pleasure at all in writing to you in these terms but I do think we are in danger of undoing all the progress we have made in the last year because the defence of the leadership election process is, at best, clumsy and, at worst, being rigged for a particular process.”

He said he had become “increasingly concerned” at the process that allows people who have signed up as a Labour Party supporter through an affiliated organisation or union to vote.

Murray said: “There is no doubt whatsoever that the way in which Unite has signed up affiliate members to vote in the leadership election is against the rules of the Scottish Labour Party and the process.

“It is important for all of us, whoever is successful, to be assured that the process is robust, fair and credible.

“As a member of the SEC and defender of the rules of the party, I think there are serious questions to answer about the sign-up process that Unite has deployed.”

He said a text message sent out by Unite encouraging people to vote for Leonard “clearly failed to ask the recipients if they supported the aims and values of the Labour Party, nor did it ask them to consent for their data to be shared with the party.

“In order for this process to be fair and robust, the party must reconsider whether any sign-ups from this process are valid.”

Murray’s letter appeared in the Herald yesterday, just hours after his own Constituency Labour Party threw their weight behind Leonard.

In total, 43 local parties backed Leonard, while just sixteen backed his rival, Anas Sarwar.

In response to Murray’s complaint, Unite said it was concerned about “repeated and underhand efforts to bring this election and our union into disrepute”.

A Unite spokesman said: “Ian Murray has been told by the SLP that our members’ affiliations are entirely legitimate. We therefore call upon him to withdraw his baseless smears now.

“Unite will be writing to the Labour party general secretary to express our concerns at these repeated and underhand efforts to bring this election and our union into disrepute.”

A senior Scottish Labour source told the Herald that Murray’s letter was a “smokescreen” to stop people asking questions about the sheer number of people signed up to the party to support Sarwar. “These are the actions of a crumbling establishment,” he said.

Reports earlier this week suggested a sizeable number of new recruits to the party have the same email address, and party insiders say they worry multiple members linked to a single email address means an individual could be taking responsibility for casting blocs of vote in the electronic ballot.

At least two secretaries of Constituency Labour Parties have raised the issue with Scottish Labour.

A spokesman for the Leonard campaign said if complaints had been made then “we expect these will be dealt with through party procedures”.

A verification panel, chaired by interim party leader Alex Rowley, has been set up to scrutinise the sign-ups.

A Scottish Labour spokesman said: “Any affiliated or registered supporter would be expected to support the aims and values of the Labour Party. These sign ups are eligible and within the rules of the leadership contest.”