Doctors are behaving unethically by not telling patients they have been paid to recruit them for drug trials, it is claimed today.

Payments from drug companies can rise to thousands of pounds per patient and some doctors are said to trawl their databases for suitable candidates for such trials.

Commercial sponsors are breaking guidelines that insist that doctors are paid for the time they spend on trial work rather than for individual patients, according to contributors to the British Medical Journal.

Jammi Rao, chairman of the West Midlands multicentre research ethics committee, and Peter Sant Cassia, chairman of the ethics committee for the University Hospitals Coventry NHS trust, say the payments could influence doctors' motives and make it more difficult for sponsors of more worthwhile research with less money to set up trials.

Some trials, especially in general practice, are designed to familiarise doctors with newly licensed drugs. "This is marketing, thinly disguised as research , and is greatly helped - and probably not possible without - a system of undisclosed payments.

"A system that allows commercially driven and clinically dubious research to crowd out good and much needed clinical trials, and that denies patients the opportunity to put their altruism to the best possible use, is unethical and unacceptable.

"Commercial sponsors regu larly flout the implicit ban on per capita payments by claiming to pay for the work involved in conducting the trial, rather than recruiting patients, and then overestimating the amount of time required for each patient ...

"We acknowledge the potential for unethical practice by requiring that the amount and basis of payments are disclosed to a research ethics committee. This does not go far enough. Not to require a similar disclosure to patients is as cynical as it demanding of unquestioning trust ...

"The attitude prevails that patients can ask about payments if it is important to them. But it is disingenuous to expect patients to know that something they have not been told anything about is important enough for them to ask about."