Plans for foundation hospitals have been narrowly agreed in the Commons, despite a huge Labour rebellion.
The plans were agreed with a majority of just 17
The controversial proposals were passed by 302 votes to 285 - a majority for the government of just 17.
The Bill now returns to the Lords where peers, who have rejected it before amid fears it will mean a "two-tier" NHS, are likely to reject it again.
There is expected to be several hours of parliamentary "ping-pong" before the Bill finally clears all its hurdles.
A total of 62 Labour MPs rebelled including ex-health secretary Frank Dobson, former international development secretary Clare Short and the chairman of the Commons health select committee, David Hinchliffe.
Long night ahead
The proposals would see some hospitals in England opting out of government control and becoming independent not-for-profit organisations.
They would be able to borrow money on the private markets and set their own financial and clinical priorities.
They would remain part of the NHS and be monitored by stakeholder councils, whose members would be drawn from local communities.
Tony Blair has been an enthusiastic backer of foundation hospitals, despite opposition from both politicians and many in the medical establishment.
Former shadow health spokesman Liam Fox said the narrow victory was a "slap in the face" for the prime minister.
"This is the smallest majority achieved while he's been prime minister. He is now no longer in control of either his party or his agenda," he said.
BBC political correspondent Mark Mardell said there was a lot of pressure on the government to get the Bill through Parliament before the current session ended on Thursday.
Otherwise it would have to be reintroduced in the next Parliamentary session, which starts next week.
A long night was ahead, he said, as another flagship piece of legislation, the Criminal Justice Bill, was also being batted between the Lords and Commons on Wednesday night.
In an earlier debate in the Commons,
Ms Short said the plans would lead to "growing inequality" because already privileged hospitals were set to benefit.
Mr Dobson said they were intended to reintroduce competition to the NHS and would set hospital against hospital.
But Mr Reid predicted that within four years the standard of every hospital in the country would be improved enough to be freed from some central control.
After the vote, he said outside the House: "I
understand that radical change is difficult but I am absolutely certain that it is for the benefit of patients and the National Health Service."
Former Labour whip Graham Allen said that although he had originally voted against the foundation hospitals bill at second reading, he had backed the government.
"This is a hopefully sobering experience for the prime minister, who must now remedy the gap between himself and his MPs with urgency," he said.
He said he had made his decision in part because he did not want to help new Tory leader Mr Howard "get off to a winning start just 18 months before a general election".
Sports Minister Richard Caborn was ordered home from Australia ahead of England's appearance in Saturday's rugby world cup final.
His place will now be taken by his boss, Culture Secretary Tessa Jowell.
Caborn: Called back from Australia
Tory health spokesman Tim Yeo said after the vote: "The government did not win this vote by persuading anyone of their case.
"They won by deploying bullyboy tactics, flying ministers from Australia, relying on Scottish Labour MPs, who will not even feel the effect of this legislation, and buying off Labour rebels by promising a 12-month review".
He described the review as "a concession which could damage any progress that foundation hospitals may make as it could deter any potential investor until it is completed."