JIM MURPHY will formally launch his bid for leadership of the Scottish Labour Party today - with an apology and a warning that the party has to change to meet the new demands of the people of Scotland following the referendum.

The Glasgow-born MP admits he has learned lessons from his 100 Streets In 100 Days Tour during the referendum campaign, when he fought for Scotland to remain part of the UK.

His official declaration will come as one of the country's leading unions backed his rival Neil Findlay, as the three candidates, including Sarah Boyack, bid to win support among elected politicians, party members and trade unions.

Mr Murphy, the MP for East Renfrewshire, said: "The referendum changed Scotland and my 100 days tour changed me.

"The places I visited reinforced my love for Scotland. But the people I met were clear what they wanted and that has left me unsatisfied and hungry for change. Scotland is my country. The country I want to lead. But if Labour wants to win we must first change ourselves.

"The Scottish people want change - they couldn't be clearer. They also want better and many want Labour to be part of that improvement."

He said: "I want to apologise because twice Scots have said they didn't think we were good enough to govern in Scotland - in 2007 and 2011. We didn't listen to them. That has to change."

Meanwhile, Aslef, the train drivers' union, backed Mr Findlay for the job, saying he had the character and vision required to win back voters who left Labour.

Mick Whelan, the union's general secretary, said: "We are supporting Neil Findlay because he has the character, vision, talent and ability to deliver for the people of Scotland. Neil understands what Labour has to do to win back the hearts, minds, and votes of working men and women."