SNP ministers have been accused of attempting to evade scrutiny of their fiscal autonomy plan by publishing North Sea oil forecasts, which show dramatically reduced estimates for tax revenues, on the last day before Holyrood's summer recess.
Opposition politicians reacted furiously after John Swinney, the Finance Secretary, issued the long-awaited figures two hours before the final First Minister's Questions, as MSPs went on their holidays.
One MSP said the move showed either contempt for parliament or the beleaguered industry.
SNP MPs will seek to amend the Scotland Bill to replace its wide-ranging package of new powers with the devolution of all tax and spending decisions north of the Border.
The policy would leave Scotland heavily reliant on North Sea revenues to maintain spending on public services.
The independent Institute for Fiscal Studies think tank has warned falling oil tax would leave a £10 billion hole in Scotland's public finances by 2020, over and above the existing deficit.
The latest oil forecasts were billions of pounds down on figures produced in May last year that were used to argue the case for independence.
The Scottish Government predicted total revenues of between £2.4bn and £10.8bn in the four years to 2019/20.
Last year's figures - forecasting a five-year period up to 2018/19 - ranged between £15.8bn and £38.7billion.
The most optimistic figure was based on oil prices climbing back to $100 a barrel immediately, a scenario dismissed by experts.
The industry itself is braced for prices to remain around their present level of about $60 per barrel for the long term.
The figures were included in the latest oil and gas bulletin, which ministers have been under pressure to update since prices collapsed in the second half of last year.
Scottish Secretary David Mundell said: "To have the latest Scottish Government oil figures published 15 months after their last update, and on the last day before the summer recess leads to suspicion that these figures aren't meant to be fully scrutinised by the Scottish Parliament."
He said it was "disappointing" for such an important industry.
He added the "central estimates on oil revenues published today are over 80 per cent lower than those they published before the referendum". He said it made the SNP's full fiscal autonomy plans even more shambolic.
He said the UK Government would reject the SNP's attempt to change the Scotland Bill, pointing out it would lead to a £10bn reduction in spending by 2020.
Jackie Baillie, Scottish Labour's finance spokeswoman, said: "It is ridiculous that the SNP tried to sneak this report out on the last day of Parliament.
"It's clear that they have put their own political interests ahead of industry concerns."
Liam McArthur, the Liberal Democrats energy spokesman, said: "Issuing this report on the day parliament rises for the summer recess either shows contempt for parliament or contempt for the oil and gas industry. The strong suspicion is that it is both."
Deputy First Minster John Swinney said the industry has faced "a very challenging year", but added: "These figures show that considerable opportunities to extend production remain in the UK continental shelf and that, properly supported, the industry can boost production over the next five years."
A spokesman for First Minister Nicola Sturgeon said: "It was published today because it was ready to be published today."
He suggested MSPs had time to digest the 20-page document.
Meanwhile, David Cameron has been accused of hoodwinking voters after the Government reset a five-year £38bn railway investment programme, the largest since Victorian times.
A Whitehall report said projects worth almost £490bn, were at risk of failing, including the flagship High Speed 2. Transport Secretary Patrick McLouglin told MPs that electrification was being "paused" on two northern routes.
Shadow Transport Secretary Michael Dugher said: "They have pretended to the public that everything was fine until after the election."
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