Many peers are expected to oppose plans to reduce their number
Justice Secretary Jack Straw has set out the latest plans for reform of the House of Lords.
Under the proposals most, if not all peers, would be elected and serve terms of between 12 and 15 years.
The Lords would be reduced in size from more than 700 peers to no more than 450. The bishops would stay, but the 92 hereditary peers would be abolished.
Mr Straw told the Commons that any change would only take place after the next General Election.
MPs voted last year in favour of a reformed Lords being either 80% or 100% elected.
Publishing a reform White Paper, Mr Straw stressed that it had never been the government's intention to legislate in this Parliament.
Instead, a package of proposals would be put to the electorate as a manifesto commitment, he said.
"The White Paper represents a significant step on the road to reform and is intended to generate further debate and consideration rather than being a final blueprint for reform," he told MPs.
Sources have told the BBC there is little appetite for pressing ahead with reform at a time of economic difficulty.
There are also several probable obstacles, including expected opposition to elections from peers themselves and the question of how to reduce the size of the Lords.
Mr Straw insisted that the Commons would retain primacy in policy and decision making.
While there would be no role for the bishops in a fully elected chamber, they would still be represented in a mainly elected House, he added, to some protests from Labour backbenchers.
Further discussion is still needed on the rights of life peers to sit and vote in a reformed second chamber, he said.
In March last year MPs voted by a majority of 113 in favour of an all-elected second chamber.
Allowed more than one choice, they also opted by a majority of 38 for 80% of members to be elected and the rest appointed.
The results of the votes were used to "inform" government plans, with Mr Straw - then the Commons leader - calling them "a historic step forward".
The previous time the Commons voted on Lords reform, in 2003, all options were rejected.
At the moment all peers are appointed, apart from the 92 hereditaries who survived the first phase of Lords reform during Tony Blair's first term as prime minister.