Party leader David Cameron has consistently resisted pressure to pledge up-front reductions, warning activists to "get used to saying 'no' more often than 'yes'."

But shadow Treasury chief secretary Philip Hammond suggested they would have to wait for at least four years after winning power before seeing promises of tax cuts.

"When the money's piled up in the pot, then you give it away in tax cuts. It only makes sense to look at this over an economic cycle," he told the Sunday Telegraph newspaper.

"You can't look at it in a single year, or even necessarily in a four-year parliament."

He went on: "We will make the savings, we will eliminate the waste and we will pile up the reserve so that at the following election, or before the following election, we are able to show people where we will make the tax cuts. It will be the great bonus of the second election."

Margaret Thatcher, he reminded Tory traditionalists urging immediate tax cuts, had also held off until she was sure they could be afforded.

Speaking at the party's spring forum in Gateshead, Mr Cameron warned: "There is not going to be some magic pot of money waiting for us when the next Conservative government is elected. So we need to get used to saying 'no' more often than 'yes'."

The Tories have a 16-point lead over Labour according to a YouGov poll for the Sunday Times newspaper, and a nine-point lead in an ICM poll for the News of the World.

The YouGov survey showed a two-point slump for Labour to 27%, its lowest share since 1983 under the leadership of Michael Foot, with the Tories on 43%, enough for a 120-seat Commons majority.