JIM Murphy has vowed to serve a full five-year term if he is reelected as MP next week, despite promising to be Labour's candidate for First Minister at next year's Holyrood elections.

The Scottish Labour leader, who had previously said he was "not attracted" to a dual mandate as both an MP and MSP, said he had told his constituents that he would not stand down from Westminster in favour of running for Holyrood.

It opens up the possibility of Mr Murphy, who was elected Scottish Labour leader in December and refused to confirm he would stand at the General Election until February, of having seats in both Westminster and Holyrood until at least 2020, should he enter the Scottish Parliament next year.

However, it is far from certain that Mr Murphy will retain the East Renfrewshire constituency he has held since 1997. In February, a Lord Ashcroft poll put him just one point ahead of SNP candidate Kirsten Oswald. A follow-up survey this month found him nine points behind the nationalists in the seat.

Mr Murphy, who is defending a majority of 10,000, said: "I have told my constituents at hustings, and I have told hundreds of people in letters, I will stay on as the member of parliament, if elected next week, for a full five years. I have been very clear about that in hustings."

Others vying for the seat hit out at Mr Murphy, claiming it would leave the people in the constituency without an adequate voice in the corridors of power.

Dr David Montgomery, East Renfrewshire candidate for the Scottish Conservatives, said: "This would mean chaos for the people of East Renfrewshire, who would not be properly represented at all under this scenario.

"How could Jim Murphy possibly do his job as MP when he's also trying to MSP for a different set of constituents and presumably chasing the job of First Minister too?"

Ms Oswald, who would claim one of the biggest scalps in her party's history if she defeats Mr Murphy next week, said: "Just a few months ago Jim Murphy was also saying that holding a dual mandate was not something he was attracted to - [this] announcement from the Labour Leader is yet more evidence that Labour cannot be trusted."

The Scottish Labour leader yesterday visited a day centre on the outskirts of Glasgow, where he remained defiant in the face of fresh polling that predicted that his party could be left with no Scottish MPs after next week.

He said: "A week is a long time in politics... we know we are behind in the polls. We have not given up on a single seat."

Mr Murphy will today reveal a new campaign poster, warning that a strong showing for the SNP and the general election could lead to a second independence referendum, which Nicola Sturgeon denies.

At the launch event, he is expected to say: "On May 7 Scotland faces two roads. It's either the road to a fairer economy with a Labour Government, or the road to a second referendum with the SNP.

"The poverty and inequality that scars Scotland won't be solved by another divisive referendum. Scotland was told repeatedly by Nicola Sturgeon that the referendum was a once in a generation event, we now need to focus on making Scotland better for generations to come. That's my promise, the SNP need to keep theirs.

"The majority of Scots don't want another referendum, and the vast majority of Scots don't want another Tory Government, but that's what could happen with a vote for the SNP. Only a vote for Scottish Labour can start us on the road to a fairer nation."