By Adam Brimelow
Health correspondent, BBC News
The target aims to speed up treatment
Doctors say a key NHS target - to treat people visiting accident and emergency units within four hours - is compromising care and patient safety.
The College of Emergency Medicine says the target, at English hospitals, puts staff under "incredible pressure".
It says it supports having a target in principle, but that doctors sometimes need time to make the right decision.
The government says safety and good quality care should always take priority over targets.
The NHS target in England to deal with patients in A&E within four hours has been highly controversial. Critics say it forces clinical staff to put deadlines before quality of care.
The chairman of the College of Emergency Medicine, Dr John Heyworth, says the target has helped to make emergency care a priority for the NHS. But he says staff are being forced to meet it at almost any cost.
"We've had nurses reduced to tears. We've had very senior consultants in emergency medicine threatened with a disciplinary process.
"This is an outrageous misuse of the standard.
"It's not what the clinicians are in the emergency departments for. But it's representative of the immense pressure being put on chief executives and all managers downwards from there to comply with the target."
The four-hour target is just one of a range of centrally imposed standards, most of them designed to speed up treatment.
They have been used in other parts of the UK but have been much more heavily enforced in England.
Politicians now dislike the language of centrally-imposed targets in the NHS.
The Conservatives and Liberal Democrats say they will scrap them. Labour now prefers to talk about "standards", "entitlements" and "guarantees". The issue promises to be an important dividing line in the general election.
Professor Julian Le Grand, who was senior policy adviser to Tony Blair between 2003 and 2005, says many patients did benefit from targets - but he recalls that the then-PM was troubled by complaints from doctors about the targets regime.
"I remember sitting in a meeting once where the prime minister said 'do we have to just keep beating up on the consultants - in A&E for instance - endlessly to achieve this? Or is there some way we can think of building in incentives within the system so that we'll get these quality improvements on their own, without always having to crack the whip?'"
That led to a shift towards encouraging more patient choice and competition between hospitals, rather than relying on targets to improve standards.
A recent analysis by the Nuffield Trust concluded that targets played an important part in making the NHS in England more efficient than in other parts of the UK.
The trust's director, Dr Jennifer Dixon, says they are a potent way of achieving quick results.
"I think there's widespread consensus that targets have resulted in immediate benefits, for example in reduction in waiting times.
"It's highly unlikely that those other reforms could have had that impact so quickly and so precisely on the waiting times. So it's really ministerial "diktat" almost that's produced the goods."
Dr Dixon thinks there could be a role for some new targets - for example, to enable more people to have their wish to die at home.
The Department of Health said that, in England at the beginning of 2003, almost a quarter of patients spent more than four hours in Accident and Emergency. It argued that since then there has been a "revolution in patient care", reducing that figure to less than 2%.
A spokeswoman said: "The funding for hospitals has risen dramatically and targets are minimum standards which taxpayers have a right to expect from NHS hospitals.
"Patient safety and good quality care should always take priority over administrative targets where a doctor believes that is necessary.
"Ministers have repeatedly said that to managers and doctors.
"All NHS providers are required by law to regard the NHS Constitution.
"The NHS Constitution includes a clear set of rights, pledges and responsibilities for staff - including no harassment or bullying, a pledge to be supported properly in a rewarding job, and the protection to speak up if services do not meet the standards we expect."
Despite his concerns over the four-hour standard, Dr John Heyworth from the College of Emergency Medicine said he had nothing against targets in principle. But he said he wanted a more sophisticated measure that accounts for quality of care, as well as speed.