The Conservatives conceded yesterday that their £4bn of tax cuts would not come into effect until next year.

Gordon Brown claimed the admission contradicted the Tories' pledge that tax reductions would be included in the party's first Budget in June if it won the election.

The Tory manifesto says: "Within the first month our first Budget will cut wasteful government spending, stop Labour's third-term tax rises and lower taxes."

But George Osborne, the shadow chief secretary to the Treasury, told Sky News that it would take the party two years to achieve its promised £35bn of savings from government waste.

On tax cuts, he said: "They come into effect in the financial year that follows. It's like all tax cuts - there's no great secret there, that's what happens, by which stage we are making significant savings in waste and inefficiency."

Osborne's comments appeared to contradict a statement by David Cameron, the Tories' policy chief.

Asked if the Conservatives could cut taxes immediately, he replied: "Absolutely. Once you set a lower path for the growth of public spending, as we have, you can do these things."

The chancellor claimed the Tories' tax and spending plans were "unravelling".

He said: "For months they have told us their first Budget would cut taxes and that pensioners would have a tax refund this year.

"Having spent months suggesting they will cut taxes immediately, the Tories are now forced to admit that they cannot find the money to do so."

But Michael Howard, the Tory leader, said Labour's criticism was "utterly wrong".

He said: "We have had these plans looked at by the Institute for Fiscal Studies, which is the independent body, the most respected body.

"They have confirmed that if we deliver on our savings, which we are determined to do, we will be able to cut taxes by £4bn in our first Budget."