Analysis By Nick Assinder BBC News Online political correspondent

It is becoming virtually impossible for any minister to get through a media interview nowadays without being asked about the prime minister's future.

Fresh talk over Tony Blair's leadership

Ever since the war on Iraq there has been widespread gossip and speculation around Westminster about his leadership.

But his about face on the European constitution appears to have shifted the speculation onto another level.

Downing Street, needless to say, dismisses all this and there is the underlying suggestion it is all being got up by the media. But that is difficult to sustain.

When senior Labour figures like Neil Kinnock openly speculate about the prime minister "hanging up his boots", that is pretty impossible to ignore.

Lost authority

Equally, when cabinet ministers do little to hide their anger at the way the prime minister handled the constitution U turn - or make it plain, albeit privately, that they are fiercely opposed to a referendum - that is bound to add spice to the brew.

But what many are now openly talking about is the fact that the prime minister, like others before him, has now lost his authority.

It is widely claimed in Westminster that the decision to hold a referendum only came after powerful interventions by the likes of Chancellor Gordon Brown and Foreign Secretary Jack Straw.

Kinnock spoke about PM's future

Similarly it is being suggested that the proposal for ID cards, which has pretty much been seen as a Blair-Blunkett pet project, has been drastically modified by ministers led by Mr Straw.

Again, all this is brushed aside, if not comprehensively rejected. But it is pretty plain there is trouble at t' mill.

Deep breath

Many Labour MPs have long been speculating about what a post-Blair world would look like.

Some claim that has now spread to ministers who are carefully positioning themselves for that day.

Home Secretary David Blunkett, while dismissing all suggestions that the prime minister is weakened and has lost his authority, appeared to confirm there were internal disputes, at least, during an interview on the Today programme.

Questioned about alleged ministerial anger at the way the prime minister executed the EU about face, he declared: "We are mature, intelligent, long in the tooth some of us, politicians. We all need to take a deep breath and look at the world outside."

Urging ministers to get back onto the domestic agenda, he added: "I hope that we can now just put this behind us and get on with the real issues that affect people's live, including campaigning for the local and European elections on 10 June."

But with Labour MPs, at the very least, looking towards a post-Blair world, that may well be a futile hope.