Chancellor says falling oil receipts are a reminder of how 'precarious' budget of an independent Scotland would be

Alex Salmond is under further pressure to publish detailed spending plans for an independent Scotland after official estimates for North Sea oil taxes were cut heavily in the budget.

George Osborne said the changes would have a significant impact on Scotland's public spending over the next two years. "The Scottish economy is doing well and jobs are being created, but this is a reminder of how precarious the budget of an independent Scotland would be," he said.

"These further downgrades in the tax receipts would leave independent Scots with a shortfall of £1,000 per person—Britain is better together."

The chancellor cited Office for Budget Responsibility forecasts that North Sea tax takings will fall more steeply than first thought over the next four years as output continues to decline. They will drop from a peak of £11bn two years ago to £3.2bn in 2016/17 – the first year of an independent Scottish government if there is a "yes" vote in September's referendum. The receipts would then rise to £3.5bn.

However, the chancellor sought to boost the UK government's case against independence by accepting industry pleas to freeze alcohol excise on whisky, one of Scotland's most valuable exports, dropping a planned duty increase.

He also scrapped the annual alcohol duty escalator, and confirmed the Treasury would support new technologies to squeeze oil from difficult reserves, while cutting several higher bands of air passenger duty – a levy singled out for abolition by Salmond after independence.

Overall, the budget had a modest effect on the Treasury grant to the Scottish government, which saw its share of UK spending increase by £68m across the next two years – a below-inflation rise on its £28.5bn budget.

As Scottish ministers insisted the OBR forecasts were overly-pessimistic, the Treasury confirmed that oil receipts are expected to fall by 24% this year to £4.7bn because of falling production and a 60% rise in capital investment.

Last year's oil receipts fell 41% on the previous year's high, leaving Scotland with a £12bn deficit, ending a long run where Scotland's overall balance sheet had been healthier than the UK's.

The OBR said it now believes oil production will flatline for the rest of the decade, even as oil prices rise slightly, leading to it cutting its tax forecasts by £8bn compared to a year ago.

Those gloomy figures were partly offset by other OBR estimates that Scotland's onshore tax receipts were expected to rise substantially from £4.8bn this year to £6.4bn in 2018/19 for the four taxes being devolved to the Scottish parliament: income tax; aggregates levy; stamp duty and landfill tax.

John Swinney, the Scottish finance secretary, said the budget was a timid and ineffective response to Scotland's needs.

Describing the whisky duty freeze as Osborne's "referendum tipple," Swinney said: "The £63m added to the Scottish budget today is small beer compared to the significant cuts Scotland has faced since 2010.

"The chancellor is planning a further £37bn of cuts across the UK over the next two years and tens of billions to come afterwards. These cuts would be worse still if Scotland does not vote for independence and Westminster takes the knife to the Barnett formula [which sets Treasury spending in Scotland]."

The Scottish government's opponents said the OBR oil tax predictions were another hefty blow for Salmond's plans for independence, raising pressure on him to explain how Scotland's high public spending was affordable if he won September's independence referendum.

Alistair Carmichael, the Scotland secretary in the UK government, said the latest data underlined how risky independence would be. "We could stop sharing with the rest of the UK and gamble on a Scotland that goes it alone. This would be a Scotland without the UK pound, a Scotland with volatile and falling oil revenues, with higher costs and with our big companies looking to leave," he said.

Blair McDougall, chief executive of the anti-independence Better Together campaign, said: "If we were independent today that would mean huge cuts to the budget for our schools, hospitals, pensions and benefits "As part of the larger UK economy we can manage this volatility without putting the funding for our schools and hospitals at risk."

Critics have rounded on the first minister's independence blueprint, as the white paper offers no detailed budgets or spending plans beyond 2016/17, while pledging to maintain free university tuition, free prescriptions, free care for the elderly and free childcare for all under-5s.

Before today's gloomier oil tax estimates, the Institute for Fiscal Studies predicted earlier this month that an independent Scotland would need to make extra £2bn cuts in public spending or raise taxes on top of expected UK-imposed cuts of £4bn, to meet the deficit left by falling oil receipts.

John Swinney did not answer demands from critics for clarity on an independent Scotland's spending, but said the new OBR and Treasury figures contradicted the UK government's whole-hearted endorsement of the predictions by Sir Ian Wood that North Sea oil production would recover in a report commissioned by UK ministers.

Swinney said the Scottish economy was very robust. The latest figures showed Scotland again out-performed the UK average with a lower unemployment rate and higher employment, while business surveys showed continuing investment and hiring in Scotland.