SCOTLAND’S biggest trade unions have given a major new boost to Richard Leonard by writing to tens of thousands of their members urging them to vote in the Labour leadership contest.

Unison and Unite have sent out mass emails telling how members of their political funds can register free as affiliated supporters and take part in the election.

They are among six trade unions to date which have declared support for Leonard. Dave Watson, head of policy and public affairs at Unison in Scotland, said: “We are writing to as many people as we can in our Labour link fund.

“We are pointing out the opportunity to register as an affiliated supporter. We show them the link and where to go to register.”

It is understood the Unison Labour link fund has tens of thousands of members in Scotland.

Watson said Unison branch organisers were also giving information to workers in local branches about how to become an affiliated supporter. A source close to Unite told The National it was also embarked on such a campaign.

“We’re doing a similar thing to Unison. If you pay the political levy you are entitled to vote in the leadership contest. But you must register as an affiliated supporter – it’s not automatic,” he said.

Leonard has insisted it will not be a trade union “stitch-up” if he wins.

At a hustings during the Labour conference, the former GMB official defended himself against accusations he would hand back control to Corbyn in London and his trade union backers.

Asked about the support of Labour’s largest affiliated union Unite, and the influence of its general secretary Len McCluskey, Leonard said: “I am delighted to receive support from all the trade unions that have declared so far.

“As for Unite’s support, it was decided after a hustings in Glasgow, it wasn’t a decision taken by Len McCluskey but by rank-and-file members in Scotland.”

Unconfirmed reports have said Unite has so far signed up more than 2700 registered supporters to take part in the contest.

Leonard is up against Anas Sarwar, whose campaign has been hit by criticism about his decision to send his children to private school and reports his family firm is not unionised and doesn’t pay the real living wage to all workers.

Union members have until October 9 to join as an affiliated supporter.

A spokesman for Sarwar said: “The Labour Party is revitalised in Scotland and we urge everyone who is part of the wider Labour family and shares our values to take part in the leadership election.

“Unison members in the health service do not need to be told how hard Anas has fought for them, successfully leading the battle to end the SNP and Tory public-sector pay cap. He has also put forward radical proposals to give local authorities a fair deal following years of SNP cuts, and will always stand up for our dedicated council workers.”