Prime Minister David Cameron held the door open for a referendum on an elected House of Lords today, as a parliamentary committee said the public should be given a say.
In a report examining the Government's reform proposals, the committee backed plans for a slimmed-down Upper House made up of 450 members, 80% elected and 20% appointed, each serving a single 15-year term and earning between £40-£65,000 a year, but said that the reforms should be put to a referendum.
But the cross-party panel of 26 MPs and peers was deeply split on several fundamental issues, and 12 members signed an alternative report denouncing the Government's draft reform Bill as unworkable and calling for the establishment of a Constitutional Convention to assess the implications of change.
With a Lords reform Bill expected to be a centrepiece of the May 9 Queen's Speech, the scene is now set for months of bitter wrangling.
Liberal Democrats regard reform of the second chamber as a key priority, and Deputy Prime Minister Nick Clegg has dismissed calls for a referendum as a waste of money.
But large numbers of Conservative backbenchers are fiercely opposed to the changes, which they fear would put the traditional primacy of the Commons at risk.
And the Bill is also expected to face stiff resistance in the House of Lords - potentially forcing ministers to invoke the Parliament Acts to get their way.
Mr Cameron today said that he was not personally in favour of a national vote on Lords reform, as it would be expensive and proposals to overhaul the upper chamber had been included in the manifestos of all three main parties.
But he refused to rule out holding a referendum - something which many of his backbenchers are demanding and which Labour leader Ed Miliband supports.
Mr Cameron told BBC Radio 4's Today programme that reforms would go ahead only if all three parties would agree to "work together, rationally, reasonably, sensibly on trying to deliver what I think the British public would see as, not a priority, but a perfectly sensible reform".
For Labour, shadow justice secretary Sadiq Khan welcomed the committee's backing for a referendum, as well as its call for the future relationship between the House of Commons and any new second chamber to be clarified.
"The proposals as they currently stand risk total gridlock in the way we are governed, something pro-reformers of all political colours will want to avoid," said Mr Khan.
"Labour supports a reformed House of Lords, through the creation of a wholly elected second chamber, with clearly identified powers, a relationship between both chambers which is codified and that upholds the primacy of the Commons, then put to the people in a referendum."
Today's report backed use of the STV system of proportional representation to elect peers, recommending a version used in New South Wales which allows voters not only to rank individual candidates but also to vote by party.
And it backed the Government's proposal for the number of Church of England bishops in a partly-elected House to be reduced from 26 to 12.
The committee agreed that the new system should be phased in gradually, with 150 members joining at each of the three general election years of 2015, 2020 and 2025. But rather than removing existing life and hereditary peers at the same rate, as the Government proposes, it argued that all those who fail to attend the Lords on fewer than one in three sitting days should be thrown out in 2015, reducing the size of the Upper House from about 800 to less than 600 at a stroke.
Committee chairman Lord Richard said: "It is now for the Government to consider our proposals before coming forward with a final Bill which it can present to Parliament for further scrutiny."
The joint committee's report revealed stark divisions between members, drawn from all sides of the two Houses of Parliament.
Nine of the 26 members voted against elected peers altogether, two voted against a 15-year term and eight voted against a referendum.
At one point, the committee was split 11-12 on whether a more assertive upper chamber would or would not enhance the work of Parliament, with a small majority deciding that it would not.
The alternative report was backed by 12 members of the committee, including six privy councillors. Among them were constitutional experts Lord Norton and Lord Hennessy, the chair of the Association of Conservative Peers Baroness Shephard, former Ulster Unionist leader - now a Tory peer - Lord Trimble, Labour MP Tom Clarke and the Bishop of Leicester.
They warned that the Government's draft Bill "totally fails" to set out a system to avoid an elected Lords challenging the primacy of the Commons.
A Constitutional Convention was needed to consider "the functions and powers of both Houses of Parliament", relations between the Commons and the Lords and Westminster's relations with devolved assemblies in Scotland, Wales and Northern Ireland following reform.
Katie Ghose, chief executive of the Electoral Reform Society, said: "It is deeply disturbing that the Committee can't seem to agree on the basic principle that we should be able to elect our representatives.
"Of course the parties don't want to lose control over who sits in the House of Lords - politicians are very good at defending the interests of politicians, but we cannot let the turkeys veto Christmas.
"If you hold the power to help decide how Britain is run you should be elected by us, the British public. That's democracy. No-one should be able to inherit or buy a place in the British Parliament."