SCOTTISH Labour leadership contender Richard Leonard is set to win the support of the UK's largest union Unite.

Unite Scotland's ruling national executive is meeting on Wednesday to decide whether to endorse Leonard or Anas Sarwar in the contest.

However, Unite sources told the Sunday Herald that the union will back Leonard, who is a leading ally of Jeremy Corbyn in Scotland.

United Left, a group of activists in the union has already voted unanimously to support Leonard.

The move came after the leader of the UK’s biggest civil service trade union also backed Leonard.

Mark Serwotka, General Secretary of the Public and Commercial Services union, voiced his support in a major boost for the Central Scotland MSP.

In an interview with the Sunday Herald Serwotka said Leonard was standing on a "very progressive" and "incredibly popular platform".

He spoke out ahead of a lecture he is to deliver in Scotland in memory of the late union leader Jimmy Reid in Glasgow on October 5.

He said he would be advising PCS members to back Leonard rather than Glasgow MSP Sarwar, who is seen as being on Labour's right wing.

The PCS is not affiliated to Labour, although Serwotka is a party member along with many others in the union.

In his 17 years as PCS leader he said that he had opposed many Labour leaders, but supported Corbyn and Leonard's agendas.

Serwotka said: "I rejoined Labour after 25 years to support Jeremy Corbyn and I was very clear in the past that my loyalty is not to a Labour Party that attacks workers.

"I'm very clear Richard Leonard is the correct choice."

When asked what he would say to PCS members, Serwotka, said: "If I was asked to give my view to members, I’d say I believe that Richard Leonard is standing on a very progressive platform like Jeremy Corbyn. It’s an incredibly popular platform."

Leonard welcomed the union leader's endorsement, saying: “Scottish Labour needs to re-forge the alliance between the party and the trades' union movement and so I am proud to have the support of trade unionists like Mark Serwotka who, day in and day out, stand up for working people.”

Meanwhile, launching his leadership campaign in Glasgow yesterday, Leonard, promised to pursue radical policies including the introduction of tough rent controls and a workers' right-to-buy should he be elected.

The Central Scotland MSP also vowed to take forward an industrial strategy which considers public ownership in the railways, Royal Mail, renewable energy and oil and gas.

He also firmly ruled out any prospect of a coalition with the SNP, telling his audience that "there will be no ground ceded to nationalism at the expense of progressive socialism under my leadership".