Senior Conservative MPs have told Sky News there is no rift in the coalition Cabinet over controversial NHS reforms.
David Cameron has insisted he is "at one" with Health Secretary Andrew Lansley and the legislation going through parliament.
Writing in The Sunday Times he also attacked Labour for "opportunism" on the issue, claiming the proposals were an "evolution" from changes introduced by the previous government.
In the last few days there has been growing pressure for the Health and Social Care Bill to be scrapped.
Several Conservative Cabinet ministers are said to have privately condemned Mr Lansley's handling of the package, with one suggesting the problems were now on the scale of the Poll Tax in the 1980s.
But Eric Pickles, Secretary of State for Local Government, told Sky's Murnaghan show the Cabinet was "united". "I've been very supportive of these measures particularly as it enhances the role of local government," he said.
Lib Dem deputy leader Simon Hughes, however, broke ranks to demand Mr Lansley be shifted from his post.
"My political judgment is that in the second half of the parliament it would be better to move on," he told the BBC's Andrew Marr show.
A Downing Street source was also quoted last week saying that the Health Secretary should be "taken out and shot".
But Mr Cameron stressed there was no alternative to reform.
The PM - whose disabled son Ivan died in 2009 - said: "As a parent, night after night, I've known what it is to have the NHS by your side.
"I've seen the dedication - the reassurance that if the worst happens, the NHS will be there for your family.
"That's why I so strongly support the founding principle of the NHS: health care for all, free at the point of use, unrelated to the ability to pay. That won't change.
"But while the values are right, the system isn't. It needs to change - and that is why I am at one with Andrew Lansley, the reform programme and the legislation going through Parliament.
"The shortcomings of the status quo are well known. There's too much bureaucracy - and too much decision-making is led by that bureaucracy rather than clinicians."
Mr Cameron said the Government was providing an extra £12.5bn in this parliament to eradicate health inequalities and cope with cost pressures.
Mr Cameron insisted the Bill gave "power to doctors and nurses", and would lead to "more choice for patients and competition for treatment".
On Friday night Labour leader Ed Miliband wrote to the House of Lords asking them to "kill the health bill".
But Mr Lansley has brushed off suggestions that it is time he resigned in order to salvage the reforms.
"No, it is not. Because actually we as a government have committed to supporting the NHS," he told reporters.
"This legislation has been supported by the House of Commons, by the House of Lords."
402 comments