By Nick Assinder BBC News Online political correspondent

Foundation hospitals is a central policy for Blair

He is also getting used to the Lords defying him by repeatedly rejecting legislation which has been passed by MPs.

What may worry him most, however, is that, in a break with tradition, Tory leader Michael Howard personally helped organise the guerrilla warfare in the House of Lords.

That suggests this particular battle of wills may go right to the wire with even the possibility that, this time, the Lords will actually defeat the government.

That would be a major boost for Mr Howard and a significant setback for Mr Blair.

Nonetheless, the prime minister will insist that his Commons victory, no matter how slim, means the government's will must prevail.

But, thanks to the backbench revolt, the Lords' opposition and the widespread feeling in his own party, Mr Blair's flagship policy is now on a life support machine.

The prime minister will also be worried that Labour backbenchers have now developed the habit of rebelling and that the size of those rebellions appears to have steadily grown.

And, of course, the key Commons vote on Wednesday night came after the foundations hospitals policy was comprehensively defeated at the party's annual conference earlier this year.

Vote of confidence

Even if he now manages to force the bill through the Lords, his fiercest critics both inside and outside the Commons will undoubtedly continue their campaign against the policy.

He will still be relieved, however, that where it really matters - in the Commons - another intensive campaign by ministers and whips to argue, persuade and terrify MPs into line did the trick.

The rebels were told that, whatever their views on the policy, a government defeat would hand Michael Howard a major propaganda coup in his first few days as Tory leader.

The whips engaged in all the usual arm twisting and threatening although it appears that, this time at least, they avoided suggesting this amounted to a vote of confidence in the prime minister.

Caborn recalled for the vote

That may have been too much of a hostage to fortune.

There were plenty of signs that ministers were worried that this core policy was about to be thrown out.

Sports ministers Richard Caborn was ordered back from Australia for the vote - needlessly as it turned out.

Serious challenge

But the move was calculated to underline the government's fears and persuade waverers to fall in line behind Tony Blair.

Some believed it was all hype designed to suggest the government was more worried than it really was.

But it is also pretty certain that, right up until the last moment, a defeat could not be absolutely ruled out.

Had the prime minister lost it would have been seen as a serious challenge to his authority and the government's central programme of reform of the public services.

He would then have faced the difficult task of deciding whether to abandon it - always an unlikely outcome - water it down even further, or press ahead regardless and potentially force a real crisis.

He will be delighted and relieved that he does not now have to make that choice - probably.

All eyes are now on the last-minute ping-pong battle with the Lords.