MRSA rates have been falling in recent years
The wisdom of screening all hospital patients for MRSA in England is being questioned by a leading expert.
Dr Michael Millar, who is involved in the screening programme at a top London hospital trust, said the tests produced too many false results.
He also said the risks and consequences of delayed operations and isolation were not fully explained to patients, the British Medical Journal reported.
But the government said screening was an important part of the MRSA fight.
It was announced by Prime Minister Gordon Brown as one of his flagship policies in the fight against superbugs - and has been implemented as MRSA rates have been falling.
All hospitals in England have had to screen patients being admitted for non-emergency surgery since April 2009.
They have until 2011 to make sure emergency cases are tested - although many trusts have already started doing this.
Most other countries, including the US, rest of the UK and much of mainland Europe, only screen the most at-risk patients, such as those who have been in and out of hospital in recent months.
Dr Millar, a microbiologist from Barts and The London NHS Trust, said that was a much more sensible policy and should be re-instated in England.
"We used to just screen the at-risk group and that was a much better way of doing it.
"The problem with screening everyone is that in low risk groups you get as many false positives as positives, if not more.
"So you have people ending up having their treatment delayed or being put into isolation when they do not need to be.
"None of this is explained to patients and I think that in unethical."
Dr Millar said part of the problem was that the NHS was increasingly relying on rapid tests, which could be leading to false positives 2.5% of the time.
That is as high - if not higher - than the rates of MRSA in the average hospital patient population, he said.
He went on to say that isolation, in particular, could have serious psychological and physical consequences.
"Research has shown that isolating patients means they have less contact with staff and family which can lead to more accidents."
Dr Millar said the focus on MRSA also meant that other infections, such as E. coli, were not getting the attention they deserved.
Dr Millar is not the first infections expert to question the screening policy.
But the Department of Health maintained it was an important part of the fight against MRSA.
A spokeswoman said: "Although the chance of acquiring MRSA is relatively low, when a patient does it is extremely distressing for them, their family and the NHS staff treating them.
"By screening patients for MRSA, the NHS is reducing a patient's risk of developing an MRSA infection themselves or passing it on to others within the hospital that may be more vulnerable."