The Government is coming under increasing pressure over its NHS reforms after doctors voted for the plans to be dropped.
Delegates at an emergency meeting said Health Secretary Andrew Lansley should withdraw the Health and Social Care Bill, and "halt the proposed top-down reorganisation of the NHS".
Some doctors support the Bill, currently going through parliament, which would see more than 150 organisations abolished and 80% of the NHS budget pass into the hands of GPs.
But many have been voicing their opposition, including to increasing the role of private companies in delivering healthcare.
The emergency meeting of the British Medical Association (BMA) comes as Labour tabled amendments to the Bill, saying there was a need to protect the NHS against the introduction of a full-blown competitive market.
The party warned this would undermine care, increase bureaucracy and put the future of hospitals at risk.
Labour also launched a petition to protect frontline services, calling on Prime Minister David Cameron to keep his promises not to waste NHS money and to protect the front line.
BMA chairman Dr Hamish Meldrum addressed almost 400 doctors at the meeting in central London, saying the Government's reforms could have "irreversible consequences".
He said the NHS was potentially facing the biggest reorganisation of its 63-year history.
"The Government's proposed reforms have far-reaching and potentially irreversible consequences for how the NHS is run and the way we deliver care to our patients."
He said it was difficult to argue against some of the Government's claimed objectives, including greater involvement of clinicians in decision-making and more information for patients.
"But, as on so many occasions, it's the reality not the rhetoric that counts and it's the reality that is causing all the problems," he said.
"Because what we have seen is an often contradictory set of proposals, driven by ideology rather than evidence, enshrined in ill-thought-through legislation and implemented in a rush during a major economic downturn."
Doctors called on the Government to act on criticisms from those who are opposed to the Bill and accept there is "no electoral mandate" for the plans.
They said Mr Lansley should "adopt an approach of evolution not revolution regarding any changes to the NHS in England".
The meeting comes after Liberal Democrat delegates rejected the shake-up at the party's spring conference, with members voting not to support the "damaging and unjustified" reforms.
Doctors also accused Mr Lansley of using "inaccurate and misleading information to denigrate the NHS", by comparing UK cancer and heart disease rates with those in Europe.
A range of other motions were passed, including one saying "enforced competition" between the NHS and private firms will lead to fragmentation of services for patients and will make it difficult for doctors to work together.
Doctors also voted against keeping details of financial transactions between private companies and the NHS secret.
On patient confidentiality, doctors said they "deplored" the lack of safeguards in the Bill for keeping patient details safe and confidential.
Dr Tony Calland, from the BMA's Ethics Committee, said the Bill enabled Mr Lansley to obtain, process and forward on details to other organisations about patients, and any social care arrangements for them, "as he sees fit".
He added: "It's rather like your bank details being transferred without your consent but it's reassuring to know they will only be used by 'nice people' who will use your money wisely."
The Government's reforms also face strong opposition from other unions, including Unite and the Royal College of Nursing (RCN).
Responding to the BMA vote, shadow health secretary John Healey said: "First the Lib Dems, now the BMA - this is quickly turning into David Cameron's worst NHS week. His damaging plans for the health service are descending into chaos."
A Department of Health spokesman said: "We are disappointed the BMA has decided to take this step, including now opposing elements of the Bill they previously supported, rather than work constructively with us to improve services for patients.
"The BMA's own survey shows their position is not representative of many of their members, who are keen to be involved in our proposals.
"The reality is over 5,000 GP practices, covering two thirds of the country, have already signed up and have started to implement plans to give patients better care."
Dave Prentis, general secretary of Unison, said: "How long can this Government go on pretending there is life in the Health and Social Care Bill? It should be pronounced DOA - dead on arrival.
"Doctors, nurses, health professionals and NHS staff have all voiced major objections to the Bill.
"Patients, charities and unions are lining up against it and poll after poll shows that the public clearly thinks it is bad news for our health service.
"And the vote at last weekend's Lib Dem conference shows they are clearly not behind it either.
"The Government is a lone voice for NHS privatisation and by turning their back on the electorate, they are turning the clocks back on healthcare across the UK."
Responding to the BMA vote, Prime Minister David Cameron's official spokesman said: "We are clearly disappointed that the BMA has decided to oppose elements of this Bill that they previously supported, rather than work constructively with us to improve services to patients."
The spokesman said the BMA's own surveys showed that today's decision was "not completely representative of its membership".Reuse content