SCOTLAND'S Deputy First Minister has challenged Labour to clarify proposals to hand the Scottish Parliament greater control of its spending if voters reject independence.

In a letter addressed to Scottish Labour leader Johann Lamont, which has been released today, Nicola Sturgeon claims there is "great confusion" about the extent of the plans and whether they can ever be implemented.

She has raised a series of questions over the assertion that Labour would make the Scottish Parliament responsible for raising 40 of the money it spends, saying answers are needed so the proposals can be "considered and debated seriously".

However, a Labour Party spokesman yesterday hit back, accusing Sturgeon of being unable to grasp the "basic proposals" of the plans, which includes control of certain tax powers and welfare budgets.

In the letter, Sturgeon argues that, using Labour's own methodology, the proposals would amount to no more than 35 per cent of devolved expenditure. And she also points out to a calculation by centre-right think-tank Reform Scotland, which suggested the proposals would amount to 26 per cent of devolved expenditure.

Sturgeon questions whether there has been an attempt to "artificially inflate", in percentage terms, the extent of the tax powers which would be in the control of the Scottish Parliament under the Labour proposals.

She adds: "If so, this would be seriously misleading and needs to be corrected immediately.

"Given the language in your recent conference speech in which you launched personal attacks on others, you will obviously want to clear this matter up as soon as possible."

The letter goes on to state: "In an independent Scotland all taxes will be under the control of the Scottish Parliament enabling any future Scottish Government to introduce policies in line with the wishes of the people of Scotland."

A spokesman for Scottish Labour said: "We welcome this new approach to asking questions by Nicola Sturgeon which doesn't involve shouting and allows people to answer and suggest she takes this style into her next TV debate.

"On devolution, the one certainty was that our proposals would not be enough for nationalists like Nicola Sturgeon who do not believe in devolution and will always put independence before the people of Scotland.

"Our devolution report was shaped by senior economists, academics and former civil servants. If Nicola Sturgeon is unable to grasp these basic proposals, how can we have any faith in her ability to create a whole new tax system in the event of a Yes vote?"

Scottish Labour endorsed wide-ranging plans for greater devolution at the party's conference in Perth earlier this month.

The party's devolution commission said the Holyrood parliament should have the powers to increase the higher rates of income tax, giving it the ability to tax richer citizens more.

Pensions and most benefits would continue to be shared across the UK, but Holyrood would gain control of housing benefit.

Speaking at the conference, Lamont said: "There is a clear message: if the people of Scotland vote to stay strong and remain in the UK, that we are voting for change."