Andrew Lansley's health reforms have been thrown into deeper crisis as a new poll reveals that nine out of ten members of the Royal College of Physicians – hospital doctors – want the NHS shake-up to be scrapped.

The findings, showing that 92.5% of RCP members want the health and social care bill withdrawn, have been passed to the Observer as the college prepares for an extraordinary general meeting on the reforms on Monday.

The bill – which is facing further trouble in the House of Lords this week, when Lib Dem and Labour peers will debate additional amendments to the section on competition – is already opposed by a wide range of bodies representing GPs, nurses, midwives and a host of other health professionals.

Tomorrow's meeting is likely to see the college agree to hold a ballot that could result in it joining other royal colleges in calling for the bill to be withdrawn.

As opposition in the medical profession increases, Lansley is struggling to maintain Liberal Democrat support for the bill during its troubled passage through parliament. Four Lib Dem peers, including Baroness Williams, will push this week for further changes with the tacit backing of the party leader, Nick Clegg, even though David Cameron warned his backbenchers on Friday that there would be "chaos" if the plans were altered further.

The overwhelming hostility of RCP members is revealed in a survey by callonyourcollege.blogspot.com, a website co-ordinating moves by anti-bill medics to persuade the royal colleges, which represent specialist groups of doctors, to reject Lansley's plans.

The site is run by four doctors who sit on the ruling council of the British Medical Association, which sparked ministers' anger last November when it became the first major medical body to adopt a hardline stance against the bill's proposed reforms. The four are acting in a personal capacity.

"This huge opposition to the health bill we see in our survey flies in the face of the rather placatory approach to the bill we have seen from many medical royal colleges in the last 18 months, including the RCP," said Dr David Wrigley, one of the site's co-ordinators. "The medical elite, close to the corridors of power in Westminster, need to take heed of grassroots doctors who have spoken out in huge numbers and said that they don't want this bill foisted on the NHS. It would be another nail in the bill's coffin if the RCP formally opposes it."

Sir Richard Thompson, the RCP's president, is under fire from some college members for attending last Monday's ill-fated Downing Street "summit" on the bill. David Cameron was heavily criticised for inviting only the small number of organisations that either back or have not rejected his restructuring of the NHS in England.

Thompson used the event to stress the RCP's concerns about the planned extension of competition in the NHS, and the potential for NHS patients to suffer as a result of the coalition's plan to let hospitals raise 49% of their income in future from private patients.

Dr David Nicholl, the doctor who collected the necessary 20 signatures of RCP members to trigger the extraordinary general meeting, said that the medical profession needed to unite to stop the "dangerous" bill.

"The bill is bad for the country's health and healthcare and will increase inequalities. None of the hundreds of amendments the government has had to table so far deal with the fundamental flaws of the bill," said Nicholl, who is a consultant neurologist at City Hospital Birmingham.

The bill will increase the number of patients being treated privately by producing longer NHS waiting times, Nicholl warned. "So why the hell are the government forcing this through? Market theory is a disaster in health. People need to stop this bill; it's plain dangerous."

The extraordinary general meeting, which is open to the RCP's 14,953 fellows, is likely to lead to a ballot of all its 26,500 members on whether it should continue "critical engagement" with ministers or move to outright rejection.

A Department of Health spokesman said: "We have already strengthened the health bill following the listening exercise and have responded directly to the points raised by the Royal College of Physicians, including clarifying that competition would only be used to benefit patients, never as an end in itself, and strengthening our plans to better integrate health services."

In another blow for the bill, an alliance of 25 health charities warns today that it could harm the NHS care received by more than two million patients with less common conditions such as neurological problems, ovarian cancer and sickle cell disease. The charities fear that the new GP-led clinical commissioning groups, which, under the bill, would assume control of commissioning treatments for patients from April 2013, will not see such patients as a priority and that services for them will be cut in a "catastrophic" blow.

Shadow health secretary Andy Burnham said: "This is an emphatic rejection of David Cameron's health bill and a clear warning to the coalition that any last-minute, self-serving deals will not be acceptable."