Gordon Brown pulled off a political coup in the House of Commons yesterday as he stunned opponents at the very end of his Budget statement with a promise to cut the basic rate of income tax next year to its lowest rate for 75 years.

Designed to wrongfoot the Tories, who have long promised to share the proceeds of growth, Mr Brown ended nearly 10 years in the Treasury with a stylish sense of drama.

He said: "I have taken 600,000 pensioners out of tax, raised child benefit in three stages to £20, cut corporation tax from 30p to 28p, increased education spending to its highest level ever. A Budget for Britain's families, for fairness and the future. And I have one further announcement.

"With the other decision I have made today we are able to hold to our pledge made at the election not to raise the basic rate of income tax. Indeed to reward work, to ensure working families are better off, and to make the tax system fairer, I will from next April cut the basic rate of income tax from 22p down to 20p. The lowest basic rate for 75 years."

Mr Brown, flanked by Tony Blair and John Prescott, sat down to rapturous cheers from Labour colleagues, many of whom had no idea how many the tax cut would affect, but had been anxiously awaiting the Chancellor's final hurrah in the Treasury.

While Mr Brown later denied he had presented a complicated Budget, such was its complexity that Mr Cameron was obliged to respond in broad-brush terms.

He accused the Chancellor of blowing open his own arguments by pledging to cut the basic rate of income tax and, in a mantra that will be heard from now until the General Election, whenever it is held, Mr Cameron charged Mr Brown with putting the tax burden up and then wasting the money.

"You are the Chancellor who has taken one tax down but put 99 taxes up. The average family is paying £1300 more because of your Budget decisions. I have to say we will check carefully what is happening to the aligning of National Insurance because we think it might be hitting middle-income families," he said.

Making one of many references to the Stalinist tendencies attributed to Mr Brown by Lord Turnbull, the former head of the civil service, on the eve of the Budget, the Tory leader told MPs: "Let me tell you what the Chancellor's real problem is. It is not that he is a Stalinist who holds all his colleagues in contempt - although I have to say that probably doesn't help - it is that he has wasted money on an industrial scale."

Sir Menzies Campbell, the LibDem leader, argued that Mr Brown had missed an opportunity. Claiming that it was the Budget of a Chancellor treading water, he said: "This is the Budget of a Chancellor ready to move on. It's a wait-and-see Budget from a wait-for-me Prime Minister. The Chancellor had the opportunity today in this final Budget to show that he was listening to the people of Britain. But he has delivered a Budget of missed opportunities.

"He had the chance to build a fairer Britain, but he has ignored it; the chance to create a greener Britain but he shunned it, and the chance to shape a prudent Britain, by saving billions of pounds on government waste, and he has avoided that too. He has spurned all of these opportunities. He has concentrated, not surprisingly, on his own political succession."

John McFall, chairman of the Treasury Select Committee, welcomed the Chancellor's focus on families, society, and business. "I think it's extremely important and welcome that he has taken 600,000 pensioners out of taxation," he said.

"He's increased child benefit and it's a Budget for business in that corporation tax has been reduced to its lowest level ever and income tax to its lowest level for 75 years."

Stewart Hosie, the SNP's Treasury spokesman, criticised the Chancellor for failing to deliver funding for a carbon storage project in Peterhead. He welcomed the new money for pensioners but pointed out a fifth of all pensioners in Scotland were in poverty.

Later, Alex Salmond, the SNP leader, accused the Chancellor of trying to con the electorate by dressing up real tax rises as a tax cut and he disputed his forecasts on oil revenue.

He said: "Brown claims oil revenues are falling. In fact they are on a rising trend, increasing from £8.1bn next year to £10.1bn in 2011/12. Over the last six years they have totalled £34bn compared with £55bn forecast over the next six years. They are only falling compared with Brown's incompetent forecasting at the last Budget. This Budget is another desperate move from a desperate Chancellor determined to try anything to hold on to power in Scotland."

John Redwood, a former Tory minister, took a swipe at the Chancellor's claims for the 2p cut in the basic rate of income tax. "It's not a cut on income tax we are being offered by this Chancellor today, it is a con, it is a small tax rise on income," he said.

"What the Chancellor gives by cutting the standard rate from 22p to 20p, he more than takes back by seizing the 10p band and removing it altogether and by raising the thresholds for National Insurance."