The BBC's Gillian Sharpe: Researchers say guidelines are effectively being ignored

The finding has led campaigners to warn against decriminalising the practice in the UK.

Voluntary euthanasia has not been a criminal offence in Holland since 1984, when courts and the Royal Dutch Medical Association drew up strict guidelines for doctors.

Dr Michael Irwin: "We have voluntary euthanasia in the UK"

However, a survey into medical practice regarding end of life decisions carried out in 1996 suggests some doctors are ignoring these safeguards.

Its findings are presented in the Journal of Medical Ethics.

Unreported cases

It found that in 1995 almost two thirds of cases of euthanasia and physician-assisted suicide went unreported.

One in five cases of euthanasia occurred without the patient's explicit request, and in 17% of such cases, alternative treatment was available in contravention of the guidelines.

Dutch law requires patients to experience "unbearable suffering" to justify euthanasia.

But more than half the doctors surveyed said the main reason given by patients for the request was "loss of dignity". Almost half said they took action "to prevent further suffering".

Dr Henk Jochensen, of the Lindeboom Institute, and Dr John Keown, of Queens' College, Cambridge carried out the study.

They conclude: "The reality is that a clear majority of cases of euthanasia, both with and without request, go unreported and unchecked.

"Dutch claims of effective regulation ring hollow."

Legal inconsistency

Another study appearing in the journal shows that the legal assessments of cases reported to the public prosecution service in the Netherlands vary considerably.

Cases are reported to determine whether a doctor will be prosecuted for murder.

Twelve hypothetical cases were presented to 47 legal assessors. Two of them would have dismissed nine of the cases from further investigation, while two would have recommended a summons in six cases.

The study was carried out by Dr Jacqueline Cuperus-Bosma, of Vrije University in the Netherlands.

The paper concluded that there is a need for clear protocols.

Euthanasia fears

Dr Peggy Norris is chairwoman of the anti-euthanasia pressure group Alert.

She said: "We need to learn from the Dutch system that euthanasia cannot be controlled.

"I know of patients in a nursing home who are carrying around what they call sanctuary certificates all the time, stating that they do not want to be helped to die.

"People are afraid of being sick or of being knocked down in case a doctor takes the decision, without their permission, to stop treatment."

'Working well'

A spokeswoman for the Voluntary Euthanasia Society said: "We would dispute some of these findings because it depends upon how you interpret the statistics.

"In Holland the majority of the public feel the system is working well."

She added: "We accept there is a problem with the levels of reporting, but that is because at the moment voluntary euthanasia is decriminalised but not legal.

"The onus is on the practitioner to prove his innocence and that does stop doctors from reporting."

Dr Michael Irwin, of the Voluntary Euthanasia Society, said the figures in the study were "old hat".