As the Labour conference prepared today for an explosive debate on the issue, a study by Philip Gould found that support for change was so soft that the battle of ideas was effectively wide open.
The research, carried out by Mr Gould and Stanley Greenberg, President Bill Clinton's former polling expert, shows that 72 per cent of the public want to ditch the current first-past-the-post system for general elections.
However, the survey reveals that such support would be "substantially eroded" once the arguments both for and against are aired in a heated referendum campaign.
The pro-proportional representation vote plummeted to 55 per cent after those questioned were told the case against reform. More than 43 per cent said they would vote "No".
Both sides in the increasingly acrimonious debate within the Labour Party seized on the research, claiming that it proved that everything was still to play for in any nation-wide poll.
Mr Blair remained vague about his own position on the issue yesterday when he said he had not ruled out holding a referendum before the next election.
However, the Prime Minister stressed that he wanted to wait for the recommendations on reform from Lord Jenkins of Hillhead, the Liberal Democrat peer, before making a decision.
"We are committed to a referendum. It has always been envisaged that we would do it this Parliament," Mr Blair told BBC Radio 4's Today programme.
Earlier, he told BBC1's Breakfast News: "My traditional position has always been that I'm not persuaded of the case for PR but I will listen to what the Jenkins report says."
A lively debate is guaranteed on the floor of the conference today, though it has become clear that Mr Blair will be spared a potentially damaging vote. The engineers' union, the AEEU, is likely to withdraw its anti-PR motion after the debate.
The anti-PR and pro-reform camps within the Labour Party showed a rare unity yesterday when they both called on the Prime Minister to allow ministers to campaign freely on the subject.
Ken Jackson, the AEEU's general secretary, was joined by leading pro- reformer, Stephen Twigg, the MP for Enfield Southgate, in calling for a referendum to be held this Parliament.
A joint statement issued by the two groups stated: "We may differ on the outcome but we strongly agree that members of the Labour Party, right the way from the Cabinet to local party members and unions, should have the right to take a view."
The widening divisions within the party have been highlighted repeatedly this week in Blackpool with Cabinet ministers coming out publicly for and against change.
Downing Street sources suggested that Mr Blair would want his Cabinet to be bound by collective responsibility on the issue once a decision has been made either way.
Officials are worried that the sight of ministers attacking each other in a lengthy referendum campaign could do the party serious electoral damage.
Yet campaigners pointed out that Mr Blair said yesterday that the Foreign Secretary, Robin Cook, was entitled to support PR if he wished.
Baroness Jay, the Leader of the House of Lords, warned yesterday that the Government was prepared to invoke the 1911 Parliament Act to push through its abolition of hereditary peers.
In her first major speech since her promotion this summer, Lady Jay said that she was prepared for a bruising battle against the "unelected, arrogant, unrepresentative" Tory peers in the Lords.
However, she also claimed that the public "don't give tuppence" about the academic debates over exactly how the second chamber should be selected.
She told a Charter 88 fringe meeting that their main interest was in scrapping the hereditary principle that blocked their elected government's mandate.
"If we have to invoke the Parliament Act, we will invoke the Parliament Act, that will only delay legislation for a year," Lady Jay said.
How The cabinet lines Up
FOR ELECTORAL REFORM
Foreign Secretary, Robin Cook; Secretary of State for Northern Ireland, Mo Mowlam; Secretary of State for Trade and Industry, Peter Mandelson; Secretary of State for International Development, Clare Short; Secretary of State for Culture, Media and Sport, Chris Smith; Minister for the Cabinet Office, Jack Cunningham; Secretary of state for Scotland, Donald Dewar; Secretary of State for Wales, Ron Davies; Secretary of State for Defence, George Robertson; Secretary of State for Social Security, Alistair Darling, and Secretary of State for Education and Employment, David Blunkett
Chancellor, Gordon Brown; Deputy Prime Minister, John Prescott; Home Secretary, Jack Straw; Chief Secretary to the Treasury, Stephen Byers; Leader of the House, Margaret Beckett; Secretary of State for Health, Frank Dobson and Chief Whip, Ann Taylor.
Prime Minister, Tony Blair; Agriculture Minister, Nick Brown; Leader of the Lords, Baroness Jay and Lord Chancellor, Lord Irvine.
Those listed as pro-reform are in favour of a variety of electoral systems, ranging from alternative vote to supplementary vote to a full PR, NOT necessarily Lord Jenkins' AV-plus system.Reuse content