Jim Murphy supporters asked to sign letter backing his leadership

Jim Murphy was elected leader of Scottish Labour in December last year

Supporters of Scottish Labour leader Jim Murphy have been asked to sign a letter giving him their backing.

The BBC understands the letter will be presented to the Scottish Labour Party Executive on Saturday, where Mr Murphy faces a vote of no confidence.

He has said he is confident of retaining the leadership, despite mounting calls for him to stand aside.

Last week's poll saw the SNP win 56 Scottish seats, leaving Labour with just one - down 40 on the 2010 result.

Former Aberdeen South MP Dame Anne Begg is thought to be among those who have given Mr Murphy their support.

She was one of 40 Scottish Labour MPs who lost their seats to their SNP in last Thursday's election.

Ms Begg said Mr Murphy was not to blame for 10 years of Labour decline.

A Labour spokesman confirmed the "letter does exist".

'Disastrous result'

He said: "There is overwhelming support for Jim Murphy across the Scottish Labour Party. We need to work together to rebuild our movement and regain the trust of the people of Scotland."

Mr Murphy earlier told the BBC he was "confident" of staying in the post despite last week's disastrous general election result.

The 47-year-old, who lost his Westminster seat to the SNP, said he still wanted to do the job.

Mr Murphy was clearing out his Westminster office when he spoke to BBC Scotland correspondent David Porter about his desire to stay on.

On Tuesday, the Labour MSP for Cowdenbeath, Alex Rowley, said the party was heading for "disappearance" in Scotland unless Mr Murphy resigned.

Pressure has been growing on the Scottish Labour leader to step down.

Both the Unite union and the train drivers' union, Aslef, have backed calls for him to go.

'Navel-gazing'

And Unison Scotland urged a "radical change in approach" by the Labour Party in Scotland and said it "would not oppose" a move to change the leader.

However, Mr Murphy has received backing from Usdaw, which represents shop workers.

The union's Scottish officer Lawrence Watson said that while the election result "could barely have been worse", to have a second leadership contest in Scotland in a year would be "navel-gazing".

Mr Watson added: "We need to keep our heads, quickly understand why the people of Scotland have, for the moment, moved away from Labour and focus on turning around the party's fortunes at the Scottish parliamentary election next year.

"Jim Murphy needs the time and our support to get the job done."

Mr Murphy had been an MP for the East Renfrewshire area since 1997.

However, when votes were counted after the close of polls last Thursday, his SNP opponent Kirsten Oswald was declared the winner.