Health Secretary Andrew Lansley was confronted by angry protesters who accused him of trying to privatise the NHS as he arrived at Downing Street to meet healthcare professionals.
One, former trade union rep June Hautot, 75, blocked his path and jabbed her finger at him as she accused him of privatising the NHS and causing longer waits for treatment.
The under-pressure cabinet minister dismissed her claims however, telling reporters after battling through the protest that they were based on a "complete misrepresentation" of the Bill.
Prime Minister David Cameron insisted he was "committed" to pushing through NHS reforms as he came under fire for excluding critics of the legislation from the Downing Street summit.
Mr Cameron accused opponents of peddling "myths" about the impact of the changes as he hailed "constructive and helpful" talks with some of those implementing the changes.
Labour leader Ed Miliband said the gathering - to which a string of high-profile professional bodies were not invited - exposed a "bunker mentality" by ministers.
He renewed demands for the Health and Social Care Bill, currently enduring a stormy passage through Parliament, to be dropped altogether and fresh reforms drawn up with professionals.
Insisting he would not be blown off course by the opposition to the reforms, Mr Cameron said: "I am committed to the changes and committed to taking them through.
"We need to do everything we can to explain to people that this is about improving and enhancing our NHS, not in any way endangering it."
"Reform is never easy, but it is vital to reform our NHS because I want it to be there looking after every family in the country and doing a good job into the future.
"We had a constructive and helpful meeting and what's clear is that there are quite a few myths that we need to bust about this reform."
The round-table discussion was designed to allow Mr Cameron and Mr Lansley to talk with chairs of the emerging GP-led clinical commissioning groups (CCGs), which are intended to give family doctors more power to help their patients choose where and when they receive treatment.
But it became a focus of anger after it emerged critics of the Bill were not invited, including four Royal Colleges: those representing GPs, Pathologists, Radiologists and Psychiatrists.
Health unions not asked to attend included the Royal College of Midwives (RCM), the Royal College of Nursing (RCN), the British Medical Association (BMA), Unite and Unison.
Royal College of GPs chair Dr Clare Gerada said ministers appeared to be "shooting the messenger" and the RCN said it was "extraordinary" not to have included critics.
Downing Street denied anyone had been excluded - saying the summit was set up to hear from "people who are implementing the reforms about how the process is going".
It said commissioning groups had described "dramatic improvements on the previous system" in the talks, also attended by leading surgeon and former Labour Health Minister, Lord Darzi.
The Prime Minister's official spokesman said that today's event was one of a series of meetings, but was unable to say whether the PM planned to meet critics of the Bill such as the BMA.
Mr Miliband accused Mr Cameron of playing "a dangerous game of divide and rule" as the scale of opposition to the Bill became clear.
During a visit to Homerton Hospital in east London, Mr Miliband said: "This bunker mentality is the wrong way to run the NHS.
"And I want to say something directly to David Cameron today - it's not too late to start listening to the doctors, the nurses and the midwives. It's not too late to listen to patients."
If passed in its present form, the Bill "will cause lasting damage to the NHS, it will divert billions from patient care and undermine our health service's basic principles", he said.
"David Cameron should drop his Bill and get round the table with everyone who cares about the future of the NHS, including those who work in the health service and other political parties."
Mr Cameron was forced to reaffirm his support for the Bill last weekend after reports that three Tory Cabinet ministers opposed the Bill and an influential grassroots website urged him to drop it.
More than 150,000 people have signed an e-petition calling for the Bill to be scrapped.
After the talks, Mr Lansley brushed off the heckling as "sticks and stones" and said the line-up for the meeting had been deliberately chosen to ensure a "constructive" approach.
In a pointed barb at some of the organisations not invited, he said: "My door is always open to the BMA, the Royal Colleges. Any time they want a constructive discussion about how we can deliver better services for patients I'm absolutely there for them.
"Some of the chief executives of some national organisations who get a lot of opportunity to sit and talk to the Prime Minister weren't there but that's because we wanted a constructive discussion which actually gave the Prime Minister the opportunity to meet people who he hadn't previously, in many cases, met in order to discuss some of these issues."