A shift away from taxes on income and wealth to "green" taxation has been promised by the Conservative Party.
George Osborne, the shadow Chancellor, declined to spell out any detail but committed a future Tory government to raise the share of revenue raised by environmental taxes.
David Cameron has resisted pressure from Tory right-wingers to fight the next election on a firm pledge to cut income tax but the proposal might allow him to do so while at the same time boosting his green credentials.
Mr Osborne said yesterday: "Conservatives should take a lead in making the changes that are needed to promote green growth. I believe we in Britain should move some of the burden of taxation away from income and capital, and towards environmentally damaging behaviour."
Ed Balls, the Treasury minister, challenged Mr Osborne to spell out whether taxes on motorists should rise when petrol prices were so high.
He said: "If you are going to be a serious opposition you need to come along and say what are your proposals, how would you pay for them, and until then people won't take you seriously."