Paddy Ashdown's MPs last night said his leadership of the Liberal Democrats would be on the line if Mr Blair refused to deliver a referendum before the next general election on the proposals due to be unveiled today by the commission, under Lord Jenkins of Hillhead, the former SDP leader.
Some Cabinet ministers, including Margaret Beckett the Leader of the House, are against a pre-election referendum, arguing that the Labour manifesto committed the party to holding a referendum but said nothing about the timing.
The Jenkins Commission will propose replacing the existing first past the post system with an alternative vote system and a top-up, elected proportionally by name in regional areas.
Mr Blair has been holding close talks with Mr Ashdown about their joint approach. He will not go as far as Mr Ashdown would like - Mr Blair is not due to announce that he has been convinced of the need for change - but he is expected to give a warm response to the work of the commission.
The Prime Minister has a difficult balancing act, with 100 Labour MPs ready to join a campaign against changing the current system to be launched tomorrow by Stuart Bell, a former front bench spokesman, with the some ministers' support. Mr Blair and Mr Ashdown would not want a referendum if the No campaign was likely to win overwhelmingly.
Mr Ashdown met his party's MPs last night at Westminster to prepare them for the announcement and Mr Blair's non-committal response.
William Hague yesterday accused Mr Blair of "fiddling with the voting system while jobs burn". The Tory leader, who will fight the reforms, said Mr Blair was "blundering into constitutional upheavals without knowing what they will lead to."
Launching his attack, the Tory leader told Mr Blair: "You committed yourself at the election to a referendum on the voting system in this Parliament. Are you still committed to it?"
Pointing to divisions within the Cabinet over electoral reform, he added:
"Robin Cook is passionately in favour of PR, Margaret Beckett, is passionately against PR and you're passionately concerned to avoid answering the question ... it's time you stopped blundering into constitutional upheavals without knowing what they will lead to."
But the Prime Minister said the Government had "always envisaged" having a referendum this Parliament but had also said that it would "wait for the Jenkins Commission to see what precise system of voting change they propose.
"I would have thought it is sensible to wait for the Jenkins Commission to report before stating a view on it," he said.Reuse content