Neil Findlay, Labour MSP for Lothians, has resigned from Labour's shadow cabinet in the Scottish Parliament

In a statement he said that Thursday's election was a "disaster" for the Scottish Labour Party, with their problems "wide ranging and deep".

Submitting his resignation from the shadow cabinet at Holyrood - where he held the fair work, skills and training brief - Mr Findlay said: "Radical solutions are needed and can only be implemented following a full, frank, open and democratic debate led by our loyal and hard working, committed party members - a centralised fix just won't do.

"I want to play a full part in that debate and in rebuilding our party from the grassroots up.

"I feel I can only do so if free rom the constraints of being a member of the Shadow Team. I have therefore today submitted my resignation from the Shadow Cabinet."

"I want to thank the Labour leadership team for the opportunity to serve the party and the movement I love."

He added that he would "redouble" his efforts working on behalf of the Lothian region.

It is understood that Mr Findlay - who lost to Jim Murphy in the contest to be Scottish Labour leader last year - has no intention of challenging for the leadership of Scottish Labour, should a vacancy arise.

In the statement announcing his resignation from Mr Murphy's Scottish shadow cabinet, Mr Findlay said he wanted to play a full part in "rebuilding our party from the grassroots up".

"I feel I can only do so if free from the constraints of being a member of the shadow team. I have therefore today submitted my resignation from the Shadow Cabinet," he said.

"I want to thank the Labour leadership team for the opportunity to serve the party and movement I love.

"I will now redouble my efforts working on behalf of the people of the Lothian region and look forward to continuing with the many campaigns I have been involved in - both outside and inside of the Scottish Parliament.

"My commitment and desire to work tirelessly on behalf or ordinary working people has grown even greater on the back of this electoral defeat. This will be my focus in the weeks and months to come."

A Scottish Labour Party spokesman said: "We are grateful for Neil's service as shadow health secretary and shadow fair work secretary. As he himself has said, the Scottish Labour Party's problems are long-standing and wide-ranging.

"We look forward to working with Neil in the coming months as we seek to rebuild our party and achieve success in the 2016 Scottish Parliament elections."

Meanwhile, Labour's leader in Scotland is being urged to resign by two trade unions in the wake of the party's disastrous results in the election.

Unite and the train drivers' union Aslef called on Jim Murphy to stand aside because it was "time for a change".

Pat Rafferty, Unite's leader in Scotland, said: "It is time for change in the Scottish Labour Party. That is the overwhelming, unambiguous message from Scotland's people, including its trade union members, on Thursday.

"Indeed, it is past time for change. Labour in Scotland has been bleeding support and credibility for years.

"On one issue after another - the embrace of 'Blairism', the opposition to a second 'devomax' question in last year's referendum, the decision to campaign with the Tories in the ill-judged Better Together campaign, and in the election of a new leader last year - Unite has warned against the course being followed by the party and has, alas, been proved right.

"The price of ignoring such warnings has been a virtual wipe-out for Scottish Labour at Westminster.

"The party has now less than a year to put this right before the Holyrood elections. Either Scottish Labour rediscovers its mission as the natural voice for social justice in our nation, or irrelevance and ultimately extinction looms."

Kevin Lindsay, Aslef's organiser in Scotland, said: "Jim Murphy has just presided over the worst election defeat in the history of the Scottish Labour Party. He has to go - and he has to go now.

"Ed Miliband, Harriet Harman, Nick Clegg, and even Nigel Farage have all stood down, accepting responsibility for, and the consequences of, defeat for their parties at the polls. It is, therefore, quite clear to most of us in the Scottish Labour Party what the right thing is for Jim Murphy to do."