A FURIOUS row has broken out over the SNP's plan to win "devo max", after the Scottish Government warned it may not reveal the radical policy's impact on Scotland's public finances before the general election.

First Minister Nicola Sturgeon said her government would publish new forecasts for Scotland's oil revenues "in due course".

However, her official spokesman later refused to confirm the figures would be issued before the general election.

Holyrood's main opposition parties all warned that Scotland's finances were under serious threat from the SNP's plans, as a result of falling oil prices.

Oil prices have become a central issue in the election fight in Scotland after Ms Sturgeon confirmed last week the SNP will demand devo max if her party holds the balance of power after May 7.

Under the constitutional set-up, also known as full fiscal autonomy, Westminster would retain control only of defence, foreign affairs and the currency.

Holyrood would take charge of all taxes in Scotland, including North Sea oil revenues, to fund public services and make a contribution towards shared UK functions such as the armed forces and overseas embassies.

The Scottish Government regularly published oil forecasts in the run-up to the referendum.

Its most recent, issued last May, predicted receipts of £20.2billion in the three years from 2016/17 to 2018/19, based on an oil price of $110 per barrel.

The UK Government has claimed that total would fall to just £1.6billion, a drop of £18.6billion, over the period if prices remain at the present level of $50 per barrel.

However, SNP ministers insist prices will recover.

But without updated tax forecasts Labour and Tory MSPs claimed voters would be in the dark about the possible consequences of devo max.

Labour, the Conservatives and Lib Dems all used First Minister's Questions to challenge Ms Sturgeon on the plan.

Responding to Tory leader Ruth Davidson, the First Minister said: "We will publish an oil and gas bulletin in due course," but she added forecasts would not be updated until after changes to the UK tax regime, expected in the Budget in March, were made public.

Pressed repeatedly after First Minister's Questions, her spokesman refused to confirm fresh figures would be issued before the election.

Ms Davidson said: "This excuse from Nicola Sturgeon about why these figures haven't been published simply doesn't wash.

"The Scottish Government published inflated oil projections in the good times, and have axed them in the bad."

Kezia Dugdale, Scottish Labour's deputy leader, said replacing the Barnett Formula, the mechanism used to share resources around the UK, with revenues raised from the North Sea would require deep spending cuts.

She said: "The SNP can't bring themselves to admit that the oil crisis is a huge threat to the money we have in Scotland to spend on our schools, hospitals and pensions.

"The Governor of the Bank of England put it best when he said being part of the UK protects our economy from the worst impacts of the oil crisis."

Ms Sturgeon hit back at the Labour and Tory claims during the Holyrood clashes.

"If their argument is that Scotland's finances are not equipped to cope with a period of low oil prices, the simple fact is that that is a direct result of decades of Westminster mismanagement," she told MSPs.

"If the problem is Westminster mismanagement, it strikes me as incredible to suggest that the solution is even more Westminster mismanagement."

The row came a day after the Governor of the Bank of England, Mark Carney, said low oil prices were a "negative shock" to the Scottish economy but the effects were "substantially mitigated" by the UK's tax arrangements.