The move is certain to be attacked by the Conservatives as an act of hypocrisy. The Liberal Democrats won the Christchurch by-election on a campaign opposing the extension of value-added tax to domestic fuel bills. Tory leaders failed to convince the voters that the Liberal Democrats were also in favour of an energy tax.
Liberal Democrats accused the Tories of confusing the taxes. But the Tories said that although the carbon tax would be levied to cut pollution from the use of carbon fuel, such as coal in power stations or petrol in cars, it could add to fuel bills.
It is one of the key proposals in an environmental green paper, Taxing Pollution, Not People, to be endorsed at the conference, which opens on 19 September.
The conference agenda, published yesterday, also includes a vote on a proposal to abolish the powers of Royal Prerogative and rules of royal succession to remove gender and religious discrimination. However, it is likely the leadership will oppose that proposal and win a majority for its package of reforms, which include a Bill of rights, freedom of information legislation, home rule for Scotland and Wales and an elected House of Lords.
The Liberal Democrat leadership appears to have succeeded in wiping out the memory of the former Liberal Party assemblies as a trial for the leadership by the anti-nuclear, sandal- wearing rank and file.
Tory and Labour conference managers are likely to look on with envy as the Liberal Democrats head for an untroubled week, discussing consumer policy, genetic engineering, the United Nations, systematic rape in war, and the future of post offices.
The conference is certain to be used by Paddy Ashdown, the party leader, to build on the party's successes in the by-elections in Newbury and Christchurch. Charles Kennedy, its president, said the party was at its highest point since the peak of the Liberal- SDP alliance in the mid-1980s.
The direction for the party will be set with a policy document, Facing up to the Future, to be published in the next fortnight. But the most glaring ommission will be any debate about the realignment of the left in British politics to oust the Tories.
Mr Kennedy said yesterday that the party conference had agreed its policy at its conference last September, when it decided to oppose formal pacts with any other party. He said that policy would not be changed.
The leadership has also defused an abortion row with David Alton, the MP for Mossley Hill. Mr Alton, an anti-abortion campaigner, threatened not to stand as a Liberal Democrat at the next election after it appeared the party had adopted a policy on abortion. The rift was patched up with a recent restatement of policy - that abortion was an issue of individual conscience. Mr Alton had refused to take on a portfolio, but yesterday it was disclosed that he would help to lead a party campaign against crime.