NICOLA Sturgeon has created an “artificial deadline” for agreeing a deal with David Cameron on new tax powers for Holyrood and is intent on crashing the process for electoral gain, senior Labour sources have claimed.

The Scottish Government strenuously denied the charge and insisted it was “busting a gut” to seal a deal on the fiscal framework, the mechanism by which the new tax and welfare powers for Holyrood will be introduced.

Labour insiders have stressed that there is no credible reason why a February 12 deadline has been set by the First Minister to allow the Scottish Parliament to pass a legislative consent motion given Holyrood is not dissolved ahead of the parliamentary elections until March 24; some 40 days later.

“There is a growing feeling that the SNP Government is simply seeking political advantage so that the Scotland Bill is not delivered to the Scottish Parliament before the elections. They are at it and are intent on deliberately frustrating the process,” said one senior Labour source.

Much of the party’s manifesto with pledges on tax, health and education, would have to be rewritten if the new powers were blocked.

The intergovernmental negotiations have been taking place for months. Another meeting of the Joint Exchequer Committee(JEC) is expected in the coming days with John Swinney, the Deputy First Minister, leading for the Scottish Government, and Greg Hands, the Chief Secretary to the Treasury, for the UK Government.

Last week after the seventh meeting of the JEC, Mr Swinney emerged downbeat, stressing how there was still a long way to go and a “significant distance to be travelled”. An SNP insider admitted a deal was now more unlikely than likely.

At the weekend, Ms Sturgeon, who famously said she wanted a deal by Valentine’s Day, warned that there had to be “significantly more movement from the UK Government than we’ve seen so far and if we don’t get that…I will not sign up to something that is unfair to Scotland”.

The deadlock centres on the complex method by which the £30 billion annual grant from Westminster will be cut after Scotland gets full control of income tax; some fear the wrong mechanism could mean Holyrood losing hundreds of millions of pounds in the coming years.

Scottish parliamentary sources said the process of scrutinising the framework could be condensed into just two weeks, if MSPs were willing to work in the evenings, meaning a deal could be struck as late as early March with the bill enacted well before the May 5 poll.

Asked if MSPs could scrutinise the legislation if a deal were done after February 12, Alex Johnstone, a Scots Tory member of Holyrood's devolution committee, said: "There is always a way.

"Trying to set an arbitrary deadline is one more tactic being used by the Scottish Government to try to force the hand of Westminster. I'm worried the First Minister is trying to stoke up more grievance while the talks are ongoing.”

Scottish Labour’s Ian Murray said he had been told that the deal was all but done but it was being blocked by Edinburgh.

“Without full transparency, it would appear to the Scottish people the SNP Government is looking for an opportunity not to implement the Scotland Bill because it’s not in its political interests to have the powers to create one of the most powerful devolved parliaments in the world.”

Meantime, a spokeswoman for Mr Swinney said "The Scottish Government is busting a gut to work with the Treasury to secure a fiscal framework by mid-February and we will continue to do so; however, we will not sign up to a deal that is unfair to Scotland.

"Achieving a deal by mid-February has been both governments’ timetable throughout to give the Scottish Parliament's committees and all parties the opportunity to properly scrutinise any agreement - something Labour have asked for - before the final vote on the Scotland Bill."