THE crisis facing Scottish Labour has been laid bare by a new a poll suggesting the SNP are on course to increase their majority at the next Holyrood election.

As nominations for the Scottish Labour leadership contest closed yesterday, a survey from Ipsos MORI showed support for the party at Holyrood has slumped to its lowest ever level.

The poll, for STV News, put backing for the SNP at 57 per cent in the constituency vote, compared with 23 per cent for Labour, among those certain to vote.

In the regional vote, the SNP enjoyed 50 per cent support, with Labour on 23 per cent.

The findings suggest the SNP would increase its number of seats from 69 to 75, while Labour would slump from 37 seats to 31.

The Tory contingent would be slashed from 15 seats to seven as their support fell to eight per cent, while the LibDems, on six per cent, would be left with just four MSPs, the poll findings indicate.

The results were based on the same poll that last week suggested the SNP were on course to reduce Labour's 41 Westminster seats in Scotland to a rump of four.

Mark Diffley of Ipsos MORI Scotland said: "These figures represent both a high point for the SNP and a low point for Scottish Labour in terms of polls we have undertaken.

"It also underlines the tough challenge faced by Labour's new Scottish leader in the months ahead in winning back some of the lost ground."

As Labour's leadership and deputy leadership contests were finalised yesterday, frontrunner Jim Murphy emerged with the most support from Labour's elected parliamentarians at ­Holyrood, Westminster and Strasbourg.

His main rival, MSP Neil ­Findlay, won the endorsement of two more trade unions - UCATT, which represents builders, and the National Union of Mineworkers (NUM) - to add to backing from public-sector union Unison and rail union ASLEF.

With nominations from 43 parliamentarians, Eastwood MP Mr Murphy said he could be a "unifying figure" for Labour.

Calling for an end to party infighting, he added: "Those days are over for Scottish Labour. This is a fresh start. Once the contest is over it's finished - no matter how individual members and trade unionists vote in this contest, we will all be on the same side.

"Each of us is determined to get rid of both the UK and Scottish governments."

Mr Murphy is the bookmakers' favourite to succeed Johann Lamont, who resigned accusing the party of treating Scottish Labour as a "branch office".

MSPs Mr Findlay and Sarah Boyack are also contesting the leadership.

Welcoming support from UCATT and the NUM, left-winger Mr Findlay said: "Justice and fairness are at the very core of my beliefs. I've worked closely with both of these unions in their campaigns to get a measure of justice for workers who have been unfairly treated simply for standing up for themselves and their colleagues."

Ms Boyack, who was backed by 10 parliamentarians, called for a "vibrant, campaigning ­Scottish Labour Party across the country".

She said: "We need to reach out to people who share our values but who haven't always voted for us."

There are also two confirmed candidates for the post of deputy leader: MP Katy Clark and MSP Kezia Dugdale.

The candidates will take part in a series of members' hustings, with the ballot opening on ­November 17 and running until December 10. The new leader and deputy are due to be revealed on December 13.

One-third of the votes will be cast by the party's parliamentarians, one-third by members of the party in Scotland and the final third by those who are members of affiliated trade unions and societies.