Chancellor George Osborne has handed the beleaguered North Sea oil industry a £1.3billion support package in his final Budget before the General Election.

He said a combination of new tax allowances and cuts - including a reduction in the controversial supplementary charge from 30 per cent to 20 per cent - would stimulate investment and increase production by 15per cent by the end of the decade.

The government will also invest in new seismic surveys of under-explored areas of the UK Continental Shelf, the Chancellor said.

In a boost to another major industry in Scotland, Mr Osborne cut duty on spirits by 2 per cent.

The move, which followed intensive lobbying, was warmly welcomed by the Scotch Whisky Association which represents distillers.

The SWA said it would take 16p off the price of the average £12.90 bottle.

Unveiling his sixth Budget Mr Osborne said Britain was "walking tall again" after presenting figures showing the country was on course to be in surplus for the first time in 18 years by 2019/20.

The UK, he told MPs, was the "comeback country".

He announced tax relief for savers and said a squeeze on public spending - amounting to £30billion - would end a year earlier than planned if the Conservatives return to power after May 7.

Ed Miliband, the Labour leader, said it was 'a Budget people won't believe from a Chancellor they don't trust".

The package of support for the oil industry came as the Office for Budget Responsibility downgraded its forecasts for North Sea revenues in a set of figures that will fuel the row between the SNP and Labour over which party offers the best hope of challenging further Conservative austerity measures.

The independent forecaster said tax take from the North Sea would slump to £700million in the coming financial year, 2015/16, down from the £2.2billion it predicted last December.

It estimated revenues for the following year, 2016/17, at £600million, down from £2.4billion. The SNP's White Paper on independence forecast Scotland would receive between £6.8billion and £7.9billion in the same year.

The OBR downgraded its forecasts for each of the next five years, wiping £9.6billion off the anticipated total tax take to 2019/20 compared with December's figures.

The figures will raise further questions about the SNP's plan to press for devo max, or full fiscal autonomy, if the party emerges from the election in a position to influence the next government.

Under the set-up, Scotland would rely on taxes raised in the country, including the North Sea, to support public spending.

The Secretary of State for Scotland, Alistair Carmichael, said: "Today's Budget is another positive step forward for Scotland in the wider journey to economic stability which has taken place over the past five years.

"It gets the important things right, with a focus on helping create a fairer and more generous personal tax system which will benefit thousands of people in Scotland and giving a helping hand to some of our key business sectors, securing jobs and prosperity for the future.

"This progress has been hard-won by this Government and builds a strong base for Scotland's economic future as part of the UK." SNP Depute Leader and Treasury spokesperson said: ''This budget fails once again to address the real needs of the people of Scotland - Osborne has blown his last chance.

"Today George Osborne could have delivered a budget focused on delivering economic growth by tackling inequality. He has not - he has decided to continue with his utterly failed austerity agenda.

''It is Osborne's Tory led coalition that have made hard working families and the poorest pay the hardest for this austerity. The Scottish Government has outlined a sustainable credible alternative to austerity - which allows for a more responsible reduction in the deficit - whilst providing real terms growth in public spending. 

Scottish Labour leader Jim Murphy said: "After five years of Tory austerity the choice facing voters couldn't be clearer.

"More cuts and deeper austerity with the Tories or a fairer deal with Labour to make work pay for working people. It is a stark choice of two different futures.

"George Osborne is a Chancellor in complete denial about the damage he has caused after five years of failing and painful austerity."

He added: "George Osborne's tax and benefit changes have cost families the equivalent of an 8p tax rise.

"On average that amounts to £1127 a year. He will leave office as Chancellor with the majority of people worse off than they were when he moved into Treasury. It's a record of failure."

Assessing the Chancellor's plans, Anton Colella, the chief executive of the Institute of Chartered Accountants in Scotland, said: "This draws the battle lines for the election. "On the one side, the claim of national recovery and growing prosperity and on the other the claim of more austerity and a Government ignoring real people's lives.

"On the whole it seems a good Budget for business but the people will decide at the ballot box whether it's done enough for them."