The Health Secretary has been confronted by angry protesters outside Downing Street claiming key organisations had been excluded from talks on the Government's controversial NHS reforms.
A small group of around 40 incensed health professionals tried to prevent Andrew Lansley from entering, jostling and jeering as he tried to placate them.
Speaking to one demonstrator, June Hautot, Mr Lansley said: "We are not privatising the NHS."
"Don't you dare lie to me," she screamed back at him.
After the clash Sky's Sophy Ridge asked the 75-year-old what she thought of Mr Cameron inviting select groups for the talks.
She said: "They (the Government) only look at the few because they know the majority are against them."
The former NHS union representative from Tooting, south London, protesting under the banner Keep NHS Public, described the encounter with Mr Lansley.
"He said, 'I want to get through' and I said 'You can wait. There's a lot of people out there waiting for treatment and if your bill goes through, they will be waiting a lot longer'."
Asked if the heckling of Mr Lansley was proof of the level of hostility to the reforms, the Prime Minister said: "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.
"Choice for patients is a good thing: making sure that GPs, not bureaucrats, are making decisions, that's a good thing.
"So there are myths we need to bust, but I also heard how, on the ground, where some of the reforms are already taking place, you are actually seeing better health outcomes, GPs doing more things for their patients, people living healthier lives as a result of these changes."
The Prime Minister and the Health Secretary chose to chair the talks with a select group of healthcare professionals at Downing Street.
The group included the Royal College of Surgeons, Royal College of Physicians, Royal College of Anaesthetists, Royal College of Paediatrics and Child Health, Royal College of Obstetrics and Gynaecology, the patient umbrella group National Voices, the Foundation Trust Network, the NHS Confederation, the NHS Alliance and the National Association of Primary Care, Clinical Commissioning Group leaders, the former Labour Health Minister, Ara Darzi, and representation from the voluntary sector by Sir Stephen Bubb.
Sir Richard Thompson, president of the Royal College of Physicians (RCP), commenting on the meeting said: "I raised with the Prime Minister our concerns that competition could damage, and is already damaging, integrated care pathways, and that the government should commit to a high quality threshold for any qualified provider for clinical services."
The gathering had attracted controversy after a number of bodies critical of the NHS reforms said they had not been invited .
The British Medical Association (BMA) and the Royal College of Nursing claimed they had been excluded from the meeting.
The BMA said it would be "odd" if organisations representing health professionals were not invited to the summit.
"The BMA does not appear to have been invited to an NHS summit at Downing Street," a spokesman said.
"If there is such an event, it would seem odd if the major bodies representing health professionals were not included."
Royal College of Nursing chief executive Peter Carter told Sky News: "We don't know why we haven't been invited but we, like others, find it extraordinary because at the end of the day, it's nurses, doctors, physios, GPs that actually keep the health service going."
The Chartered Society of Physiotherapy, which opposes the bill, said it, too, had been excluded from the meeting.
Phil Gray, its chief executive, said: "If new legislation is to succeed it is vital that those raising concerns are listened to and it is disappointing to see that so many organisations are being shut out of the process."
Labour leader Ed Miliband said: "You don't get progress on the NHS by shutting the door of Downing Street on doctors, nurses and patients' groups.
"It's not the actions of a Prime Minister to exclude from an NHS meeting the people who are the experts on the health service."
More than 147,000 people, including footballer Rio Ferdinand and TV star and author Stephen Fry, have signed an e-petition calling for the bill to be dropped.