Scottish Labour leadership candidate Anas Sarwar has called for the "spirit of the rules" of the contest to be respected amid claims there could be a trade union stitch-up in favour of his rival Richard Leonard.

The Jeremy Corbyn-supporting Mr Leonard said he was "delighted" to have received support from all the unions that had so far declared, including Unite, the UK's largest.

He said the rules of the leadership contest had been agreed and it was wrong to "call foul" after the decisions had been taken.

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The two rivals to replace Kezia Dugdale were taking part in a hustings at the Labour Party conference following a report in the Huffington Post that Unite had signed up 2,700 members to the union's political levy - a payment that makes them eligible to vote in the leadership contest - in just two days last weekend.

in The Herald today, we reported sources close to Mr Sarwar warning that Scottish Labour activists "wouldn't take kindly" to any attempt by Unite to return the party to "a branch office".

At the hustings, Mr Sarwar said he wanted more people to join Labour or sign up as supporters in order to vote in the contest.

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But he added: "Through that process we have all got to make sure we play by the rules - that's in terms of the written rules and also the spirit of the rules as well.

"As long as all of us do that I have no problem with more Unite members or any other trade union members joining this process, voting in this contest and hopefully then engaging with us as well as we return a UK Labour government and also a Scottish Labour government, too."

At the hustings in Brighton, organised by the Daily Record, Mr Leonard said: "The trade unions are going through due process of deciding who it is they are going to back and I don't think it's right to call foul about those rules after decisions have been taken.

"If there's a problem with the rules you should say that there is a problem with the rules up front."

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He added that Unite's support came following a hustings and it was "not a decision taken by Len McCluskey", the union chief who is close to Mr Corbyn, but rather by the "rank and file" of the organisation in Scotland.

At the Brighton event, Mr Sarwar said he would not be afraid to clash with Mr Corbyn if it was in the interests of Scotland.

"That's not to say we are going to pick deliberate fights with the UK Labour Party of Jeremy Corbyn," he said.

"It's about saying in a grown-up environment, with an autonomous Scottish Labour Party not being a branch office ... that we can take different decisions in Scotland that are right for Scotland's interests."