A leaked internal Labour document has prompted the SNP to say it is winning the argument on Scottish economic policy.

As the parties continue to battle it out ahead of May's elections to the Holyrood parliament, a confidential Labour document was reported to admit that the economic message from the nationalist party was "clearer, stronger and more consistent".

"Labour are losing the economic argument because they refuse to recognise that Scotland lacks the powers it needs to influence our economy," said SNP leader John Swinney.

"As a result, Scotland continues to bump along with an appallingly low growth rate."

His campaign was boosted by the leaked document, disclosed in the Scotland on Sunday newspaper, which was prepared for enterprise minister Iain Gray.

Gray, who is writing the party's manifesto, has also been the victim of speculation suggesting he could be moved from his current post.

The SNP said the leak of the document was part of an attempt to blame the minister for the poor performance of the Scottish economy.

"The repeated leaks and heavy spin against enterprise minister Iain Gray shows that far from offering solutions, Labour is now playing a blame game," said Swinney.

"With just weeks to go before the election, Jack McConnell and his lieutenant Andy Kerr are obviously trying to scapegoat the enterprise minister in a pathetic attempt to shift the blame.

"Firing Iain Gray, however, will do nothing to improve our economy. We have to do more than simply dump failed ministers; we also have to dump the failed policies they have pursued."