Jim Murphy ditched his Westminster shadow cabinet post yesterday as he scrambled to secure the Scottish Labour leadership in spite of union opposition.

The Blairite stood down as shadow international development minister, saying: “I want to dedicate myself full-time to changing Scotland and changing the Scottish Labour Party.”

Mr Murphy cast off his Westminster duties a day after Unison became the latest union to throw its weight behind left-wing candidate Neil Findlay.

The public-sector union backed Scotland’s shadow health minister after he debated Labour’s future with leadership rival and fellow MSP Sarah Boyack at a hustings organised by the union on Saturday.

Speaking afterwards, Scotland Labour Link chairman Gordon McKay said: “Neil understands that politics as usual isn’t good enough and we believe he offers a fresh approach with a real experience and understanding of the concerns of working people.

“At today’s meeting Neil Findlay outlined a radical new policy approach that will be welcomed by our members.”

Mr Murphy was dealt another blow after skipping the hustings to launch his own campaign with a speech in Edinburgh.

Unite Scotland secretary Pat Rafferty said members would find it difficult to “find much to find hope that Jim Murphy is offering the genuine, positive change in Scottish Labour they seek.”

His statement follows the endorsement of Mr Findlay by train drivers’ union Aslef on Friday and rail union TSSA on Saturday.

Scottish Labour’s leadership will be decided by an electoral college, in which votes are split equally between elected members, trade unionists and party activists.

Mr Murphy told Radio 5 Live yesterday that winning over the union’s was “a job for another day.”

He said he wanted to “pick the Labour Party up” but polling by YouGov shows that the SNP would benefit most from Mr Murphy’s leadership.

Support for Nicola Sturgeon’s party leaps from 43 per cent to 47, while Labour would receive a 2 per cent lift from 27 to 29.