Insisting that a Tory government would "move towards lower taxes", George Osborne has said it is "very unlikely" the party would promise tax cuts at the next general election.
Speaking in Manchester, the shadow chancellor criticised Gordon Brown for a creating a tax bill he said was £219bn higher this year than when Labour took power.
"Where once we had one of the most competitive corporate tax regimes in the developed world, we now have one of the least," he said.
"So I am clear. We need to move towards lower taxes."
But Osborne said that because the Treasury was predicting a budget deficit of £24bn in 2009, the likely date of an election, it would be irresponsible for the party to promise tax cuts.
"That will be a disappointment to a few in my party. They think the key to winning general elections is to make up-front promises of tax cuts - even though we have fought the last three of them on that promise and lost all three of them," he said.
Outlining the Conservative policy of "sharing the proceeds of growth", he said a Tory government would take a "long-term, sustainable path to lower taxes".
"As the economy grows, and revenue flows into the exchequer, we will share the proceeds of that growth between improving public services and reducing borrowing or lowering taxes," said the shadow chancellor.
"Over an economic cycle, the state will consume a smaller share of national income."
He said the party hoped to take on "powerful vested interests who jealously guard the reliefs and tax breaks they have won for themselves".
And he proposed a programme of "tax simplification" to remove complexity and unfairness in the system.
Responding to the comments, chief secretary to the Treasury Stephen Timms said: "George Osborne seems to be totally confused. First he proposed a flat tax. Then he promised a combination of lower taxes and lower spending.
"Now he is promising lower spending on public services but no reduction in taxes, which is the worst of all worlds, and pledging to cut tax credits, which would make up to six million families worse off.
"The Tories will never gain trust of the British people if they continue to change their economic policy from one day to the next."
Liberal Democrat treasury spokesman Vince Cable said: "The Tories’ commitment to simplify - but not reduce - taxation is more spin without substance.
"Making our tax system simpler is not enough. We need it to be fairer and greener too. There must be a very substantial reduction in taxes on people’s income and moves towards taxing pollution. It is unacceptable for low and middle income families to contribute a higher percentage of their earnings than the most affluent in society."
