NICOLA Sturgeon has said she is 'highly sceptical' about fracking, as she attempted to counter claims the SNP was preparing to give the go-ahead to the controversial gas extraction technique after the Holyrood election.

The First Minister was accused of misleading voters in the run up to the May 5 poll by promising 'no fracking in Scotland' while only a temporary ban remains in place.

She ducked questions on her long-term commitment to the government's moratorium from Kezia Dugdale, the Scottish Labour leader, who announced a toughening of her own party's position against fracking.

But, in a bid to close down the row, her chief political spokesman later revealed the First Minister was personally "highly sceptical" about the practice.

"Unlike Kezia Dugdale we will continue to be led by the evidence.

"That's why we are taking forward a very detailed process of assessment while the moratorium is ongoing.

"But the First Minister is highly sceptical about fracking".

He said her position was based on "publicly available information", though a detailed report for the Scottish Government in 2013 found fracking was safe.

The temporary ban, imposed last October, will be in place until at least next year when scientific reports are published.

Ms Dugdale claimed the SNP was preparing to give the controversial gas extraction technique the green light after that.

Ms Dugdale said the Scottish Government's decision to look into the future decommissioning of fracking plants was evidence of its intention to allow the practice.

She also cited comments by Jim Ratcliffe, boss of Ineos, the company which wants to frack across parts of central Scotland, who last year told The Herald the Scottish Government had privately reassured him it was not against fracking.

Ms Dugdale said the SNP's 'no fracking' claims could not be trusted after it this week broke a 10-year pledge to scrap the council tax

She said: "The SNP say fracking is bad.

"They have imposed a temporary freeze.

"A big report has been ordered. But it looks like they are going to go ahead and do it anyway.

"All across the country SNP candidates are telling voters that there will be no fracking under the SNP."

The row dominated clashes during First Minister's Questions, when Ms Dugdale challenged Ms Sturgeon to commit to a permanent ban.

Ms Sturgeon said: "We won't allow fracking in Scotland because we will not take risks with our environment when there are still unanswered questions.

"That's why we have a moratorium in place."

She later repeated her pledge that there would be "no fracking in Scotland because there is a moratorium on fracking," adding: "That's what 'moratorium' means."

At the last election Scottish Labour said it would give local communities the chance to vote in local referendums on fracking plans in their area.

But pledging an outright ban, based on growing concerns about climate change caused by burning fossil fuels, Ms Dugdale vowed: "Scottish Labour will go into the election with a very clear manifesto commitment.

"We will oppose fracking.

"A moratorium is not an outright ban; it’s only a temporary stoppage.

"Her maybes aye, maybes naw response can mean only one thing – Nicola Sturgeon plans to give the green light if she is re-elected in May."

Environmental campaign group WWF Scotland welcomed Scottish Labour's promise to ban fracking.

Director Lang Banks said: "We welcome the strong commitment made by Kezia Dugdale that Labour would introduce an outright ban on fracking and other unconventional fossil fuels in Scotland.

"The party's very clear position reflects what climate science tells us and the overwhelming public opinion in favour of cleaner forms of energy.

"The Scottish Government's current moratorium on fracking is not the same as permanent ban, as we've consistently called for it to become."

He added: "As we fast approach the Scottish elections, we call on each political parties to keep their promise to publish a manifesto that delivers on the Climate Change Act. "We need to hear from each of Scotland's parties how they plan to deliver on their promise to cut emissions and secure the benefits of low-carbon Scotland."

Friends of the Earth also backed the move.

Patrick Harvie, the Scottish Greens leader, said: "Scottish Greens led Holyrood’s first debate on fracking, calling for a ban, in May 2014.

"MSPs from all parties voted against it.

"Labour’s sudden conversion a few weeks before an election is late but welcome."