The Conservatives have pledged to raise the inheritance tax threshold to £1m.

Setting out his party's plans for "the most important reform of capital taxes for a generation", shadow chancellor George Osborne also said a Tory government would abolish stamp duty for first-time buyers on homes costing less than £250,000.

He told the party's conference in Blackpool on Monday that his plans would take 10 million people out of "these taxes on aspiration".

He said: "When inheritance tax was first introduced it was designed to hit the very rich. But the very rich hire expensive advisers to make sure they don't pay it.

"Instead, thanks to Gordon Brown, this unfair tax falls increasingly on the aspirations of ordinary people.

"So now well over a third of homeowners in Britain have the threat of inheritance tax hanging over them."

In a warmly-received speech to activists, Osborne also promised that the Conservatives "will always be looking for ways to bring taxes down".

But he reiterated the party's commitment to two per cent a year spending rises for public services for the next three years.

The Tories would "share the proceeds of growth", he said, and make sure the economy grew faster than the size of the state.

And he said he would adopt the policy, recommended by John Gummer's quality of life policy review group, to replace air passenger duty with a tax on flights.

This would mean empty aircraft pay the same as full ones, and would penalise older, more polluting planes.

He dismissed one of the group's more controversial proposals, for a charge on supermarket car parking, with a joke, asking if the conference hall thought he was "off my trolley".

And Osborne also announced a new £25,000 annual levy on wealthy people living in Britain and registered for non-domiciled tax status offshore, estimated to raise £3.1bn.

The charge would be "easy to administer, difficult to avoid and strikes the right balance between a fair tax system and a competitive economy", he said.

"We have a new dividing line in British politics," he went on.

"The dividing line between a Labour prime minister who has taxed a generation out of home ownership and a Conservative government that will abolish stamp duty for first-time buyers.

"The dividing line between a Labour prime minister who penalised couples and presides over social breakdown, and a Conservative government that supports marriage and encourages families to come together.

"The dividing line between a Labour Party that punishes those who aspire for a better life and a Conservative government that says clearly: We are on your side."

Shadow business and enterprise secretary Alan Duncan earlier said Gordon Brown had "squandered a decade of growth and set aside nothing for a rainy day".

"He has built his political success on the illusion of unending prosperity, using it as an instrument for his own selfish advance instead of as a foundation for the country's future," he said.

"Brown is the man who has doubled your council tax and destroyed your pension. He is the man who has presided over a collapse in saving and an astronomical explosion in personal debt."

Duncan promised to cut red tape for business by ensuring that for every new regulation introduced, two or more existing rules would be scrapped.

And the department he shadows would, he said, become a champion of small businesses and British interests abroad.