The Royal College of Physicians (RCP) has dropped its opposition to assisted dying and adopted a neutral stance on the issue.
A poll of almost 7,000 UK doctors found that 43.4% felt the RCP should oppose any change in law, while 31.6% were in favour of supporting assisted dying.
The RCP said a failure to get a 60% majority either way means it will now adopt a neutral stance on the issue.
Four medics have said they will seek a judicial review over the poll, but the RCP said this was rejected by the High Court on Thursday.
The last time the RCP surveyed its members on the issue was in 2014.
At that time, 24.6% wanted the RCP to support a change in the law, rising to 31.6% in the latest poll.
The latest survey also asked fellows and members whether they personally supported a change in the law on assisted dying.
Those supporting such a change increased to 40.5% from 32.3% in 2014, while those opposing it fell from 57.5% to 49.1%.
The percentage saying that if the law changed they would be prepared to participate in assisted dying increased from 21.4% to 24.6%.
The percentage saying no fell from 58.4% to 55.1%.
RCP president, Professor Andrew Goddard, said: “It is clear that there is a range of views on assisted dying in medicine, just as there is in society.
“We have been open from the start of this process that adopting a neutral position will mean that we can reflect the differing opinions among our membership.
“Neutral means the RCP neither supports nor opposes a change in the law and we won’t be focusing on assisted dying in our work.
“Instead, we will continue championing high-quality palliative care services.”
Sarah Wootton, chief executive of Dignity in Dying, said: “It is highly significant that the oldest medical college in England has dropped its longstanding opposition to assisted dying in favour of a neutral position.
“This will allow the RCP to accurately reflect the range of views among its members and to contribute its expertise to the debate in a more balanced way.
“The RCP will now join the Royal College of Nursing, the Royal Society of Medicine and medical associations around the world which have taken a balanced and compassionate stance on this issue.”
Baroness Finlay of Llandaff and Lord Carlile of Berriew, who co-chair Living and Dying Well, said only 25% of respondents to the RCP poll said they wished the college to have a neutral position.
They said: “No-one will be surprised by the outcome of this poll, the rules for which were changed to involve a significant departure from those governing previous consultations and which were set, under pressure from campaigners for assisted suicide, in such a way as to produce the result they have.
“In fact, more RCP members and fellows voted for the college to oppose assisted suicide than voted for neutrality. But as a result of the recent arbitrary and politically motivated change in the rules, their views have been ignored.
“The change in voting rules, which was made without any consultation or authorisation from RCP members, has understandably attracted widespread criticism, prompting the former chair of the college’s ethics committee to describe this consultation as a ‘sham’.
“Since the consultation’s inception, the potential for voting irregularities has also come to light, casting further doubt on the credibility of this entire exercise.
“Campaigners for assisted suicide may try to claim that the consultation shows a shift in medical opinion on this highly-charged matter.
“In reality it cannot be regarded as a serious expression of medical opinion and it has damaged the college’s reputation as a professional body.”