DAVID Mundell wants to scrap the February 12 deadline for concluding talks to deliver more powers to the Scottish Parliament.

A senior Whitehall source branded Nicola Sturgeon’s desire to reach agreement by Valentine’s Day “a red herring” while another made clear the Scottish Secretary wanted the deadline pushed back to February 22 “to maximise the chance” that London and Edinburgh could get a deal.

Labour insiders have claimed the February 12 deadline – set so MSPs have time to scrutinise any agreement – is artificial given there are a further 40 days until Holyrood is dissolved on March 23 ahead of Scottish Parliament elections in May.

They have accused the First Minister and her colleagues of being intent on crashing the process for political gain; a claim strongly denied by Ms Sturgeon.

During a Commons debate on the so-called fiscal framework, the mechanism by which the new powers will be implemented, the Scottish Secretary responded to Labour calls to drop the deadline, telling MPs: “I don't think in terms of self-imposed or arbitrary deadlines.

"Personally, keen though I am to have a warm and supportive relationship with the Scottish Government, I have never felt the St Valentine's Day date had much relevance to this process. I'm willing to continue working towards a deal as long as that takes and as long as we can.”

A source close to the Secretary of State explained: “He wants the deadline put back to maximise the chance of reaching a deal. Holyrood goes into recess for a week immediately after February 12 so it would make sense to set a deadline as soon as MSPs return.”

Extending the deadline to February 22 would allow five weeks for the Holyrood committee scrutinising the Scotland Bill to hear evidence from key players and assess the deal before a final vote by MSPs. The legislation must be approved by them before the powers can be transferred ahead of the election campaign, which begins on March 24.

In a parallel development, Mr Mundell announced the House of Lords debate on the bill, scheduled for next Tuesday, had now been put back to February 22 to “ensure both the Scottish Parliament and the House of Lords have as much information as possible for their consideration”.

The Commons debate was opened by Labour’s Ian Murray, who said Scots were being "locked out" of the discussions and that light needed to be shed on the "very secret" talks.

“It is simply unacceptable that the process of redrawing Scotland’s fiscal terrain is taking place behind closed doors,” declared the Shadow Scottish Secretary.

But Stewart Hosie, the SNP’s deputy leader, argued that it was “absolutely right” the negotiations were undertaken in private.

"Imagine if there's a running commentary and slight snippets of information, out of context, simply become the fodder of a new Labour Project Fear campaign…We want to see, instead of sniping from the sidelines, a Labour Party determined to support fair play, a fair settlement and one which actually delivers to the principle of no detriment."

His SNP colleague Deidre Brock warned the UK Government that the Holyrood elections would be defined by the Scottish people "setting their face" against it if a deal were not reached.

But Labour’s Kevan Jones claimed that whatever happened the SNP would conduct the May election with a "victim mentality" rather than setting out what it would do with the new powers.

Earlier, Greg Hands, who is leading for the UK Government in the talks, told the Commons Scottish Affairs Committee that he too disagreed with the February 12 deadline, declaring he was “ready to deal”.

Stressing how he remained “hopeful to confident” that an agreement could be reached, the Chief Secretary to the Treasury told MPs that he had cleared his diary so that he could travel to Edinburgh on Monday for his ninth meeting with John Swinney, the Deputy First Minister, who is leading for the Scottish Government.

Giving evidence, Mr Hands stressed how there was “no academic consensus” on which of three mechanisms was best to establish the framework but strongly indicated the UK Government was against the per capita index deduction model favoured by Mr Swinney and in favour of the so-called levels deduction, which the SNP Government claims would cost Scotland £7 billion over 10 years.

The Treasury chief highlighted the view of Oxford academic Professor Jim Gallagher, who argued the Scottish Government’s demands, if realised, would be unfair to the UK.

“But,” explained the minister, “he went on to say and this is very important: ‘It would be hard to explain to English taxpayers…that, if their population grows, they must provide services for them but also send some of the tax these taxpayer pay to support additional services in Scotland, where the population has not grown.’”

Asked by the SNP’s Pete Wishart if he personally supported the levels deduction option, Mr Hands replied that, overall, this “best answers” the Smith Commission.