Gordon Brown will include House of Lords reform in his election manifesto, justice secretary Jack Straw has told MPs.
Mr Straw said the government was determined to reform the House of Lords and would be seeking cross-party consensus.
The justice secretary told the Commons he wants to remove the "anomaly" of hereditary peers.
Attempts to reform the House of Lords have been problematic, especially amid resistance from the second chamber.
In March, MPs voted for a wholly or 80 per cent elected chamber, but Lords said they should be appointed and not face a public vote.
Mr Straw promised a "comprehensive reform package" and said a cross-party group will begin work on constitutional change.
Progress in these talks will determine whether a white paper can be published before the election, which could potentially be called as early as 2008.
However, the Conservatives have said the plans are effectively "on ice" until after Mr Brown calls a general election. David Cameron himself has said he would not address Lords reform until his third electoral term.
Mr Straw said the government would not rush through reforms, insisting there was "some way to go" and stressing the need for consensus.
He told the Commons: "In dealing with such a central element of the constitution it is right that there's as much all-party agreement as is possible.
"I accept there may well not be total agreement, but the constitution does not belong to any one party and it should not be used as a partisan tool."
Nick Herbert, the shadow justice secretary, said he would work with the government to achieve consensus. However, he said the reforms were effectively on hold until the next election.
The Conservatives are also cautious about what reform will entail.
"We cannot accept the removal of the independence and authority of the present Lords unless real democratic accountability is put in its place," Mr Herbert said.
Speaking for the Liberal Democrats, Simon Hughes said he welcomed a commitment to reform and promised to help reach consensus.
But Mr Hughes criticised any further delays and insisted it was now time to get on with the process of reform.
Mr Hughes said: "If Gordon Brown and Jack Straw want to be remembered for delivering a new constitutional settlement fit for the 21st century, then they must get on with the job.
"Reform of the Upper House started nearly 100 years ago and is now within our grasp. We must make sure that we not only deliver the changes, but enshrine them in a way that cannot be undone."
Mr Straw also said he would look at whether it could be possible to strip convicted criminals of their peerages.