The Health Secretary hit back following reports of criticism from Tory Cabinet colleagues over his handling of the shake-up.
Asked if it was time he resigned in order to save the changes, Mr Lansley told journalists: "No, it is not. Because actually we as a government have committed to supporting the NHS.
"This legislation has been supported by the House of Commons, by the House of Lords."
Commenting after delivering a speech in Edinburgh, Mr Lansley went on: "It is not about the Bill as such, it is about what the Bill enables the NHS to achieve in the future.
"That is not about me, that is about us as a government."
He added: "It is because the NHS matters so much, because we believe in the values of the NHS, we have to be prepared to reform."
The latest wave of speculation over Mr Lansley's future was sparked when Tory grassroots site ConservativeHome claimed three Cabinet ministers had privately "rung the alarm bell" about the shake-up.
One apparently called for the health secretary to be replaced, another said the Bill should be dropped, and the third likened the NHS reforms to the poll tax.
Editor Tim Montgomerie wrote: "David Cameron's greatest political achievement as leader of the opposition was to neutralise health as an issue.
"The greatest mistake of his time as Prime Minister has been to put it back at the centre of political debate."
Party co-chairman Baroness Warsi and health minister Simon Burns were quickly mobilised to try to shore up Mr Lansley's position.
Mr Burns told BBC News: "To be quite frank, they are all unnamed - I regard it as tittle-tattle.
"From what I see within the parliamentary party and from my conversations with ministers, they are very fully supportive because they understand the need for the NHS to modernise to make sure that patients are at the centre of decision-making about their health."
However, the row showed little signs of abating. Earlier this week an unnamed Downing Street source was reported as saying the health secretary should be "taken out and shot" for mishandling the policy. David Cameron was perceived to have offered Mr Lansley only lukewarm backing when the issue was raised at Prime Minister's Questions on Wednesday.
The Government has already "paused" the Health and Social Care Bill and accepted dozens of amendments since it was first introduced.
But the concessions have failed to quell protests from professional bodies such as the British Medical Association and the Royal College of Nursing.
The legislation has already suffered one defeat since reaching the Lords and there are fears that the process could drag on into next month.
In his speech today, Mr Lansley said: "As some of you may have heard, we're making a few changes south of the border. Giving patients more control of their own healthcare will embody the principle of shared decision making."
He added: "We're putting clinicians in charge, free from burdensome top-down, process-driven controls...I do believe we are about to see a huge upward shift in quality in the NHS in England."
Mr Lansley said his reasons for trying to modernise the health service are "very simple".
He said: "I want patients in the NHS to enjoy outcomes, results, that are consistently among the very best available anywhere in the world."
Shadow health secretary Andy Burnham said: "We already know that the Prime Minister isn't listening to doctors and nurses. But it's a shock to find out that even senior members of his own Cabinet have to take to a Conservative website to get through to him about the damage he is doing to the NHS."
Labour leader Ed Miliband said: "Nurses, doctors and patients have been telling David Cameron for months that he's on the wrong track on the NHS.
"Now even members of his Cabinet are telling David Cameron that he is making a profound mistake on the NHS.
"I think what this shows is a Prime Minister who, every day that he presses on with this Bill, is increasingly out of touch with everyone
who cares about the NHS.
"He should drop this Bill which is wasting billions of pounds on a
bureaucratic reorganisation and threatens a creeping privatisation of our National Health Service."
PA
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