Paddy Ashdown has put his future as Liberal Democrat leader firmly in the hands of the Labour party.

In an end-of-conference speech which was critical to his battered authority, he told delegates he would never back down from his demands on Labour for voting reform.

He threw down a direct challenge to Tony Blair to deliver a referendum on proportional representation for Westminster elections and a freedom of information bill.

And he signalled the controversial alliance between his party and the government would collapse if he failed.

He also pleaded with his delegates not to abandon him now, when their great ambition was within their grasp.

Conference suspicious of Blair

He won no applause when he declared he respected Tony Blair for introducing devolution in Scotland and Wales, a bill of rights and an independent central bank.

But there were shouts of 'hear, hear' when he demanded to know whether the prime minister was ready to change his view and back PR, whether he was a "pluralist or a control freak."

Delegates are deeply suspicious of the alliance and are only sticking with it - and with Mr Ashdown - in the hope they will win the ultimate prize of PR.

And that is why their leader's future now hangs on the decision of the parliamentary Labour party.

Why bother with co-operation?

They are not a happy bunch at the moment. Many, probably most, don't want PR and don't believe Mr Blair needs to continue cosying up to the Liberal Democrats and offering voting change as the carrot.

With an historic Commons majority, which under most systems of PR would have been vastly reduced, they find the alliance baffling.

And next week, at the Labour party conference in Blackpool, Mr Blair will come under intense pressure to abandon it - and with it his manifesto commitment to voting reform.

It will certainly be a test for the prime minister, but it will be an even bigger one for Mr Ashdown.

Where now for Ashdown?

He did all he could to prove to his own party that he would never abandon the demand for reform - but the issue is effectively out of his hands.

And he knows that, if Labour MPs manage to block the change, he will be out on his ear. Any number of his MPs are waiting in the wings including Charles Kennedy, Simon Hughes, Don Foster and Malcolm Bruce.

He even managed a joke at his own expense on the issue declaring: "There is something I want to say to you about retirement ..."

Turning to his MPs sitting behind him he added: "Steady lads, steady. They are behind me so I know I'm safe."

He also acknowledged the concern of his own party over the alliance with Labour, saying: "Perhaps I'm being a bit unkind to Labour in this speech - but I don't suppose you will think so."

Win reform or step down

Most delegates later accepted he had done the only thing he could. But many also thought his speech was otherwise lacklustre and lacking in fire.

Others speculated that the strain of 10 years as leader, and the punishing pace he sets himself, were finally starting to show.

Bermondsey MP Simon Hughes summed up the overwhelming view by insisting that his leader's position was now dependent on voting reform.

He insisted it was the country through a referendum, rather than the Labour party, that would decide the issue.

But it is clear that, if Labour fails to deliver that referendum before the next election, Mr Ashdown's position will be untenable.

"I thought that was a statesmanlike speech and a unifying speech, and I am not a sycophantic poodle about leaders' speeches," said Mr Hughes.

"At the end of the day, he made the only point he could to Tony Blair. So nobody can complain that wasn't a clear statement of his position.

"But we have always known that, if a leader who sets his sights on the big breakthrough and the referendum doesn't deliver, his future will be an issue.