Oil revenues would have made Scotland a powerful player in Europe

The information was kept confidential at the time to keep Nationalism at bay.

The paper was obtained by the Scottish National Party under freedom of information legislation.

Written by a leading government economist in 1974, it sets out how oil would have given Scotland one of the strongest currencies in Europe.

The report by Professor Gavin McCrone also stated that Scotland would have had "embarrassingly" large tax surpluses.

'Industrial desert'

But Dr McCrone's projections for independence were kept secret because of Labour's fears about a surge in SNP popularity.

The report shows officials advising ministers about how to take "the wind out of the SNP sails".

This is a fundamental lie that the people of Scotland have been spun for 30 years Kenny MacAskill SNP

Kenny MacAskill, of the Scottish National Party, said the report was proof of 30 years of official lies, cover-ups and betrayal.

He added that it showed how much Scotland would have benefited from independence and oil.

He said that in the 30 years since the report, Scotland had suffered low economic growth and manufacturing decline while at the same time oil wealth had "transformed" Canadian provinces and Arabian shiekdoms.

"Some have chosen when they've discovered oil to make the desert bloom and the tragedy was that in 30 years in some areas of Scotland, the UK Government has created an industrial desert," he said.

Service cuts

Mr MacAskill insisted that, with prices rising rapidly, oil was now "on the agenda" and he claimed an independent Scotland "would never be richer".

He added: "I would first of all like to have an apology from the UK Government for lying to us.

"We're not talking about something that's negligible.

"This is a fundamental lie that the people of Scotland have been spun for 30 years - that we were too wee, we couldn't do it, that the oil was going to run out - when they knew for 30 years that Scotland was sitting on a bountiful presence that would have transformed our economy for the better."

However Scottish Secretary Alistair Darling dismissed the document.

He said: "This is typical of the Nationalists, looking back to the past. This document is 30 years old.