LABOUR have called for an investigation after accusing the SNP of sneaking out a crucial report into the oil industry on last day before Holyrood's summer recess.

A new Oil and Gas Bulletin, which opposition parties had called for repeatedly over recent months, was published at 10am on Thursday. It showed significantly lower estimates of North Sea tax revenues, reflecting a declining oil price and leading to claims the SNP's case for full fiscal autonomy had been significantly weakened.

Jackie Baillie, Labour's finance spokeswoman, has written to outgoing Scottish Government Permanent Secretary Sir Peter Housden asking when Ministers were first sighted on drafts of the bulletin and when the decision was made to publish it. She branded the timing of the report "a scandal" amid claims the move was intended to escape parliamentary scrutiny.

Ms Baillie added: "The SNP Government's latest Oil and Gas bulletin is a game changer. After months of denouncing everybody and anybody who said their sums don't add up, the SNP have finally admitted themselves that their sums don't add up. The SNP's economic case for independence and full fiscal autonomy now lies in tatters.

"That such an important moment in the debate about Scotland's future was dealt with in such an underhand and cynical way is a scandal. It discredits Nicola Sturgeon's claim to lead an open and transparent government."

The Scottish Government said it would consider the letter once it is received. In the bulletin, the Scottish Government predicted total revenues of between £2.4 billion and £10.8 billion in the four years to 2019/20.

Last year's figures - forecasting a five year period up to 2018/19 and used to argue the case for independence - ranged between £15.8billion and £38.7billion.

A spokesman for John Swinney, the Deputy First Minister, branded Labour "pathetic". He said: "If we had waited until the summer recess to publish, they would be moaning about that. The paper was published with parliament in session and a full two hours before First Minister's Questions - where they chose to talk about macaroni pies instead. If Labour can't fully digest a 20-page document in two hours on an issue that is already well rehearsed, then it calls into question their competence or how seriously they take the issue.

"The report itself shows that Scotland remains, by some margin, the biggest oil producer in the entire European Union - and no other country in such a position would have it suggested that it could not finance itself."