An extraordinary alliance of over 100 Labour MPs, Cabinet ministers and trade unions was building with business chiefs and the Tory leadership to stop electoral reform.
The chairman of the Labour First-Past-The-Post group, Stuart Bell, a Labour backbencher, said he had already held talks with Michael Ancram, the chairman of the Tory Party, and Liam Fox, the Tory spokesman on constitutional affairs.
He said two-thirds of the Cabinet were against reform including John Prescott, the deputy Prime Minister, Margaret Beckett, Leader of the House, Jack Straw, the Home Secretary, Ann Taylor, the chief whip, and Derek Fatchett, the Foreign minister, whose boss, Robin Cook, the Foreign Secretary, is one of the few ministers actively supporting electoral reform.
"This is the one issue that unites the Tory Party," said Mr Bell. "In the Labour Party, if there were to be a referendum we would have a united Tory Party fighting a divided Labour Party on electoral reform."
John Redwood, the shadow trade secretary, said: "This is a really lethal split. It seems the bulk of the Labour Party and the Cabinet is against electoral reform."
Mr Blair has told the Cabinet not to "raise the banner for one side or the other" over electoral reform, but Mr Bell said that the attempt to force the Cabinet to toe that line would fail.
Mr Bell welcomed the support offered by William Hague for the cross- party alliance to block the Jenkins report - which wants to bring in a two-tier system of MPs, with over 100 MPs elected proportionately for county areas and large towns and cities alongside the MPs for constituency seats.
Mr Hague said: "We will work with Labour MPs, trade unionists and all groups in society who are willing to stand up for strong, democratic Government."
The Labour campaign against the Jenkins report was being spearheaded by money from the Amalgamated Engineering and Electrical Union led by Ken Jackson, which has already spent pounds 10,000 on the launch.
But Mr Bell said business leaders and other trade unions would be prepared to foot the campaign bill of around pounds 200,000 to keep the first-past-the- post system and match the amount of money being used to back the pro-reform campaign "Make Votes Count'. He claimed that the Joseph Rowntree Trust was paying pounds 100,000 towards the reform campaign.
Challenging Mr Bell to "put up or shut up" about the MPs who oppose electoral reform, the "Make Votes Count" campaign, last night, named their senior business backers including Lord Haskins, the chairman of Northern Foods, Sir Adrian Cadbury, Sir Peter Parker, Hugh Morgan Williams, chairman of Canford Group, Sir John Harvey-Jones and Anita Roddick.
The scene is already being set for a knock-down battle between the "yes" and "no" camps over the referendum, which is now almost certain to be delayed until after the general election.
The hostility to the Jenkins report will surface in the Commons next Thursday in a full-day's debate, without a vote.