Major professional bodies have confirmed they have not been invited to talks with the Prime Minister over the Government's controversial NHS reforms.
The Prime Minister 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.
The architect of the shake-up, Health Secretary Andrew Lansley, felt the hostility of some campaigners as he was jostled and barracked on his way into Downing Street.
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.
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."
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.
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". The Prime Minister's official spokesman said the 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.