LABOUR will seek to challenge the SNP over its policy of full fiscal autonomy as MPs debate the Queen's Speech today.

It is understood that Labour will attempt to amend the Scotland Bill to include a review into the impact of devolving all tax and spending decisions to Holyrood.

Labour plan to call on the SNP's 56 new MPs to back the probe, which would look at the costs of the policy, as well as its consequences for both Scotland and the rest of the UK.

Economists have suggested that the powers could leave Scotland almost £8 billion a year worse off, a figure the SNP disputes.

The SNP are expected to use the debate to push for extra powers for Scotland, arguing that the current Bill, based on the cross-party Smith Commission proposals, does not go far enough.

The party has faced accusations from opponents in recent weeks that it is backing away from the controversy surrounding full fiscal autonomy.

Deputy First Minister John Swinney said on Sunday that the party acknowledged in its manifesto that the policy would take "some time to deliver".

The SNP would "consider and put forward a range of propositions extending to full fiscal responsibility", he added, but there were other powers that could be delivered more quickly.

Earlier this week Scottish Liberal Democrats challenged the SNP to bring forward detailed amendments to the Scotland Bill to create a Scottish Full Fiscal Autonomy Bill.

The SNP are expected to call on ministers to demand the early devolution of the national insurance contribution.

Ahead of the debate, Labour's shadow Scottish secretary Ian Murray has also called for powers over the Work Programme, the government's back-to-work scheme, to be given to local authorities in Scotland.

The moves by Labour come as former Scottish leader Johann Lamont called on the party to take time to reflect on its catastrophic election defeat if it wanted to survive.

Ms Lamont said that the scale of the thumping had been worse than anyone "possibly imagined" as she called for Scottish Labour to now elect a leader "for the long haul" to recover.

Her successor Jim Murphy resigned after just months in the job in the wake of the party's defeat in Scotland, in which he also lost his own seat.

The SNP won 56 out of the 59 constituencies in Scotland, while Labour slumped from 40 seats to just one.

The next leader of the party in Scotland also faces a race to turn around the party's electoral fortunes before next year's Scottish Parliament elections.

Ms Lamont said: "Even those of us who were preparing for the worst possible defeat couldn't possibly have imagined what happened. We couldn't have predicted it, but we need to analyse it if we're going to survive.

"The instinct of the Labour Party is if there's a problem, change the leader, then sit back, fold your arms and wait to be disappointed because they're sure it's not going to deliver.

"We can't do that this time. We need to elect a leader not on a short-term contract, but a long-term appointment for the long haul.

"There is no quick fix to this, there are not any ploys, not any gimmicks, that will get us through the next period.

Ms Lamont also said that SNP leader Nicola Sturgeon "shone" during the General Election campaign.

She said the SNP had provided "a lesson in how to run a campaign", and Ms Sturgeon had been "completely in control".

But her intervention was rejected by some senior Scottish Labour figures.

One said that she should stop, adding: "She pressed the nuclear button as she walked out the door."

Ms Lamont, MSP for Glasgow Pollok, resigned as leader last October accusing Westminster Labour of treating Scotland like a "branch office".

One UK Labour leadership contender, Yvette Cooper, will travel to Scotland this week as part of her "win back" campaign.

In Glasgow she is expected to meet around 50 people who voted Labour in 2010 but have since supported the SNP.