Nine out of 10 hospital doctors - members of the Royal College of Physicians (RCP) - want the NHS reform to be scrapped, according to a survey leaked on Sunday.
The study shows that 92.5% of RCP members want the Health and Social Care Bill withdrawn, according to the Observer, which said it had seen the findings.
The report comes on the eve of the RCP's emergency meeting to discuss the controversial reforms.
The leadership of the College has been coming under pressure from some members over its willingness to continue negotiations with ministers on the Bill.
Last week, more than 30 fellows and members of the College wrote to the Daily Telegraph saying its president, Sir Richard Thompson, should not have accepted an invitation to a Downing Street summit last Monday.
Andrew Lansley was heckled in Whitehall by protesters, including a woman who described the health secretary's reforms as "Codswallop".
On Friday of last week Lib Dem President Tim Farron said the NHS Bill should have been either substantially changed or dropped, in a clear sign of festering resentment among his party.
Tomorrow afternoon the RCP will hold an extraordinary general meeting (EGM) of fellows to discuss the Bill.
There will also be a vote on whether to survey fellows and members on whether they accept or reject plans laid down in the Bill.
No decision on the RCP's position will be made on the day.
The Observer said the overwhelming hostility of RCP members was revealed in a survey by callonyourcollege.blogspot.com, a website coordinating moves by anti-Bill doctors to persuade the royal colleges to reject the reforms.
The site is run by four doctors who sit on the ruling council of the British Medical Association, who are acting in a personal capacity, the newspaper said.
Dr David Wrigley, one of the site's coordinators, told the newspaper: "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."
An RCP spokeswoman said today: "Tomorrow at our extraordinary general meeting we will discuss whether to formally survey all our 26,000 fellows and members on their views about the Health and Social Care Bill.
"The RCP continues to have serious concerns about the reforms and has been lobbying vigorously for changes to the Bill since its publication."