Accident and emergency patients could be being put at risk by the need to meet the government's four-hour waiting target, senior doctors claim.
The doctors say they want a lower target
Half the casualty units in England told the British Medical Association pressure to meet targets meant patients were moved inappropriately.
Some 40% also admitted patients were discharged from A&E before they had been properly assessed or stabilised.
But the government said the survey painted a "distorted picture".
The government had set down a target which said that, by the end of December last year, 97% of patients should be seen, treated and discharged from A&E within four hours of being admitted.
Half failed to meet the target.
The government has said that by March this year an extra 1% should be seen within that time.
Prime Minister Tony Blair has agreed that the four hour target may be too rigid but insisted it had helped promote improvements in "pretty ghastly" A&E units.
He said: "Most people would say the accident and emergency departments today are a lot better than they were.
"We feel, and maybe we are wrong, that one way we've managed to do that is by setting a clear target.
"But maybe we need to look at how we have sufficient flexibility in the targets."
One hundred and sixty-three of England's 200 casualty units responded to the BMA's survey.
Many said the four-hour target had improved care for A&E patients, and welcomed the focus on emergency care.
But 27% said care of seriously ill or injured patients was compromised by pressure to meet the target.
Eighteen percent said patients were "admitted" to A&E instead of to a ward so they could be counted as being transferred.
However, 90% of A&E consultants said that they backed the four-hour target, but believed it had been set too high.
They said a lower target of 95% would give doctors the ability to allow those patients who need to be in casualty for longer than four hours to do so, without coming under pressure to move them from managers.
Donald MacKechnie, chairman of the BMA's A&E committee, said: "It is absolutely right that patients visiting A&E are seen and treated as quickly as possible but not if staff are being forced to make inappropriate decisions and patient care is any way compromised."
He added: "I am appalled to hear that some A&E staff are being put under intolerable pressure, even bullied, by their trusts as they attempt to treat and discharge patients within four hours."
The honorary secretary of the British Association of Emergency Medicine, Steve McCabe said while many patients would agree A&E has improved, there is a percentage of patients whose care is jeopardised.
"I have heard of examples of patients who have deteriorated because of pressure to reach targets and moving them out of the department.
"And some patients may have died as a result. I don't think there's any question about that."
Health Minister John Hutton said: "This BMA survey gives a deliberately distorted picture of the changes that have taken place in A&E Departments. NHS patients tell us that A&E is better than ever."
He said any doctor with a genuine concern about patient care or fiddling of figures had a clinical duty to speak to trust managers, their Strategic Health Authority or the Department of Health.
Mr Hutton added: "To date we have received no formal complaints."
Shadow Health Secretary Andrew Lansley said: "Time and again we have warned the government that the waiting list targets would distort clinical judgements and put patients at risk.
"The government have never listened."