ALEX Salmond's claim that Scotland is poised for a new oil boom has been dismissed as "wishful thinking" after Budget figures downgraded forecasts for North Sea revenues.

New independent figures predicting the North Sea will generate up to £24 billion less than Scottish Government estimates sparked angry clashes following George Osborne's statement.

In a separate row, Finance Secretary John Swinney accused the UK Government of "deceit" and "baloney" over claims the Budget would give Scotland extra spending power.

SNP ministers came under pressure after the independent Office for Budget Responsibility lowered its predictions for North Sea tax take by nearly £1bn over the coming five years.

According to Budget figures, the OBR now believes oil and gas will generate £33bn up to and including financial year 2017/18 – £24.1bn less than the Scottish Government's best case scenario.

The figure – revised down £0.9bn since December – is £8.5bn lower than the Scottish Government's most cautious estimate, published in a controversial report earlier this month.

The report had allowed the First Minister to proclaim an oil boom days after a leaked cabinet briefing paper revealed Mr Swinney's private concerns about the state of the economy and the affordability of pensions and unemployment benefits under independence.

But Scottish Secretary Michael Moore said: "There is a gulf between those independent OBR figures and the hugely optimistic numbers published by the Scottish Government last week.

"This debate must be based on fact, not wishful thinking."

Labour's Shadow Energy Minister Tom Greatrex said: "The fact that oil and gas revenues are expected to fall by 40% this year confirms that although the industry remains an important part of the Scottish economy, it is a declining and volatile resource."

The SNP Government defended its own forecasts, saying: "OBR projections continue to be lower than many industry forecasts."

Mr Swinney, meanwhile, accused the UK Government of "deceit" over claims the Budget would leave the Scottish Government £176 million better off over the next two years.

The Scotland Office said the Scottish Government would lose £103m from its resource budgets – cash used to fund services – over the next two financial years, as a result of the extra squeeze on public spending announced by Mr Osborne.

But it claimed the cash would be more than compensated for by Scotland's £279m share of additional capital spending, or cash earmarked for non-recurring projects. The Scotland Office insisted the cash amounted to "additional spending power" but Mr Swinney said: "That is a deceitful claim."

He said the additional funds would come as loans for first-time homebuyers and to fund building as part of a programme outlined by the Chancellor. Mr Swinney added: "I would call this loans and equity. You might call it funny money.

"Anyone who says this increases my spending power is deceiving the public. It's not free for me to use. It does not increase my spending power. It will never appear in my Budget."

STUC general secretary Grahame Smith also dismissed the extra investment, describing it as "wholly insufficient".

He said: "Given that any consequentials to Scotland will at least partially be offset by spending cuts, the STUC expects any stimulatory effect to be insignificant in economic terms. However, the additional pain for those affected by the cuts will be very real."

Margaret Curran, Labour's Shadow Scottish Secretary, said: "The Chancellor has failed all his key tests.

"He had an opportunity to give a budget for jobs and growth. He could have reversed the tax cut for millionaires and introduced a VAT cut which would have given a real boost to the Scottish economy.

"But instead we have more policies that are going to hit hard working families."

Her comments were echoed by a host of third sector organisations. John Dickie, head of the Child Poverty Action Group Scotland, said new discounts for childcare would disproportionately benefit the better off.

Judith Robertson, head of Oxfam Scotland, welcomed the decision to ensure the UK met foreign aid pledges, saying the move would save lives.

But she said: "Raising the tax threshold will do almost nothing for those on the lowest incomes and indeed offers more to higher earners."

Margaret Lynch, chief executive of Citizens Advice Scotland said that for hard-pressed families "the misery will not only continue, it will get worse".

Scotland's business organisations were supportive of the Budget. David Lonsdale, assistant director of CBI Scotland, welcomed "solid growth-enhancing measures". He added: "The Chancellor is right to continue the path towards balancing the government's books and beginning to pay down the ballooning national debt."

Colin Borland, of the Federation of Small Businesses' in Scotland, said: "The Chancellor's decision to help the smallest employers, and prospective employers, should not only benefit these businesses but will give a welcome boost to the Scottish job market in 2014."