Commons leader Jack Straw has said he doubts reform of the House of Lords will be completed before the next general election.
Mr Straw said there was a 'huge amount of work to do'
He told the Commons Constitutional Affairs Committee there was a "huge amount of further work to be done".
But he added: "Is it my determination we should proceed? Absolutely."
In March MPs voted for an 80% to 100% elected second chamber but peers rejected the plan, opting to keep a fully appointed house.
Other options included a 50-50 elected and appointed split.
Mr Straw, who prefers an 80-20 split, told the committee there was "an unexpectedly good degree of consensus" .
"We're not going to get total agreement within each party. The constitution doesn't belong to any one party and it should not be used as a partisan tool."
"Moving with deliberate speed" is the best way of achieve "what most of us want" which is either a substantially or wholly elected chamber, he said.
On the likelihood of the Lords accepting reform, he told the MPs: "If we take this steadily, I think they will in the end."
But he said he did not want to "rush the fences" on a reform programme that he said had been under consideration since 1909.
Asked if the government would use the Parliament Act to force reform through in spite of Lords opposition, Mr Straw replied: "You can never rule it out."
His appearance comes a day after Prime Minister Tony Blair said MPs should be "cautious" before trying to "replicate the Commons in the Lords".
Mr Straw also said there was no need for a written constitution, although there "may come a time" for one.
Chancellor Gordon Brown, who will become prime minister in days, suggested in May that Britain could get its first written constitution, saying: "We need a constitution that is clear about the rights and responsibilities of being a citizen in Britain today."
Mr Straw, who is Mr Brown's leadership campaign, is expected to play a key role in the new Brown Cabinet.