TREASURY Chief Secretary Danny Alexander says Alex Salmond's credibility on the economy has received another "body blow" after official figures showed tax revenue from North Sea oil and gas fell by £800m in 12 months.

Figures released by Her Majesty's Revenue and Customs showed corporation tax revenues from the North Sea dropped from £4.4 billion in 2012-13 to £3.6bn in 2013-14.

They followed on, the Treasury pointed out, from figures published in June, which showed overall tax revenues from oil and gas fell from £6.1bn in 2012-13 to £4.7bn in 2013-14; a reduction of £1.4bn.

Reacting to the latest figures, Mr Alexander said: "These are another body blow to Alex Salmond's credibility on the economy.

"They follow on from Sir Ian Wood's devastating criticism that the Scottish Government has wildly overstated oil reserves. On the very day Alex Salmond is promising enhanced child care they show a significant downward trend in oil-related tax revenues."

The Highland Liberal Democrat MP insisted the figures added to the overwhelming evidence Scotland could better afford the quality public services it deserved if it remained part of the United Kingdom. "Mr Salmond is guilty of promising the Earth, but not having the oil and tax revenues to pay for it," said Mr Alexander.

However, Scottish Energy Minister Fergus Ewing hit back, saying: "It's come to a sorry pass when Danny Alexander is boasting North Sea tax receipts have fallen on his watch.

"He was the man who boasted about his idea to introduce the disastrous 2011 supplementary charge, which damaged the industry, so it is perhaps not surprising."

Mr Ewing said the statistics showed why Scotland needed to take the stewardship of the oil and gas industry away from the UK Government.