A DEVO max Scotland would be £7.6billion worse off next year, according to a devastating new report from the respected Institute for Fiscal Studies (IFS) think tank.

The study warned a fiscally autonomous Scotland, relying entirely on taxes raised North of the Border, would require deep spending cuts unless the price of oil recovered or the economy grew much faster than the rest of the UK.

The figures - which took into account the Office for Budget Responsibility's (OBR) latest oil forecasts - came as the Scottish Government refused to say when it would publish its own assessment of the country's finances.

First Minister Nicola Sturgeon yesterday conceded that oil predictions in the SNP's independence White Paper last year - which were 13 times higher than the latest OBR forecasts, were "wrong" but, under pressure from opposition MSPs, said updated figures would be published "as soon as possible".

Her official spokesman later refused to guarantee that revised figures would appear before the General Election in May.

In its Budget report, the independent OBR wiped billions of pounds off the expected tax take from North Sea oil over the next five years.

Over the period 2015/16 to 2019/20, total revenues were put at £3.5billion - down by £9.6billion on previous estimates - as the impact of lower oil prices and Chancellor George Osborne's new tax breaks were felt.

The IFS said the slump would leave Scotland's finances in a worse state compared to the rest of the UK.

It said Scotland's deficit as a share of gross domestic product would be 8.6 per cent next year, more than twice the 4 per cent forecast for the UK, equivalent to £7.6billion in cash terms.

The figure was £1billion worse than a previous forecast last week, before oil revenues were revised down.

Another economic think tank, Fiscal Affairs Scotland, forecast an even wider gap, equivalent to nearly £8billion in 2015/16.

The figure means Scots would be £1485 per head worse off under devo max, the think tank said.

Scottish Labour seized on the figures to launch a fresh attack on the SNP's plan to demand devo max, or full fiscal autonomy, if it wins a share of power in May's election.

Speaking during First Minister's Questions, deputy leader Kezia Dugdale said Ms Sturgeon should admit that switching from the Barnett formula, the mechanism used to distribute funding around the UK, to devo max would devastate Scotland.

She told MSPs: "Last week I said scrapping Barnett would cost Scotland £6.5 billion in spending cuts.

"I was wrong. The oil projections from the OBR confirm the costs would now be £7.6 billion.

"That's a Barnett bombshell. It would mean billions of pounds worth of cuts."

Ms Sturgeon accused her of "pouncing gleefully" on bad news.

She insisted "our public finances are improving," citing Fiscal Affairs Scotland figures showing a £15billion increase in tax revenues, excluding oil, over the next five years.

However it later emerged the total was more than offset up by increased spending and falling oil revenues.

Scots Tory leader Ruth Davidson hit out at Ms Sturgeon for calling on voters in England to vote for the Greens, after party leader Natalie Bennet criticised the Government's £1.3billion support package for the North Sea oil industry.

"Can I ask why a First Minister of Scotland is telling people in England to vote for a party that would kill Scotland's oil industry?" she said.

Ms Sturgeon said: "Dearie, dearie me. "Just for the benefit of Ruth Davidson and indeed for anybody else across this chamber I'm Nicola Sturgeon, I live in Scotland, I'm voting SNP and I encourage everybody else to vote SNP as well."