Four times in recent months, Dutch doctors have administered lethal doses of drugs to newborns they believe are terminally ill, setting off a new phase in a growing European debate over when, if ever, it’s acceptable to hasten death for people who are critically ill.

Few details of the four newborns’ deaths have been made public. Official investigations have found that the doctors made appropriate and professional decisions under an experimental policy allowing child euthanasia that’s known as the Groningen University Hospital protocol.

But the children’s deaths, and the possibility that the protocol will become standard practice throughout the Netherlands, have sparked heated discussion about whether the idea of assisting adults who seek to die should ever be applied to children and others who are incapable of making, or understanding, such a request.

“Applying euthanasia to children is another step down the slope in this debate,” said Henk Jochemsen, the director of Holland’s Lindeboom Institute, which studies medical ethics. “Not everybody agrees, obviously, but when we broaden the application from those who actively and repeatedly seek to end their lives to those for whom someone else determines death is a better option, we are treading in dangerous territory.”

The Dutch debate is being closely watched throughout Europe. Belgium has laws similar to those in the Netherlands, and a bill permitting child euthanasia is before its parliament. No date has been set for debate.

Britain is considering legalizing assisted suicide for people with terminal illnesses, amid reports that doctors already may be helping thousands of patients to die each year.

“Assisted dying is a fact,” said Hazel Biggs, the director of medical law at the University of Kent, who is about to publish a report estimating the number of assisted deaths in Britain at 18,000 annually. “We have to regulate it, to ensure that vulnerable people are being protected.”

Under the Groningen protocol, if doctors at the hospital think a child is suffering unbearably from a terminal condition, they have the authority to end the child’s life.

The protocol is likely to be used primarily for newborns, but it covers any child up to age 12.

The hospital, beyond confirming the protocol in general terms, refused to discuss its details.

“It is for very sad cases,” said a hospital spokesman, who declined to be identified. “After years of discussions, we made our own protocol to cover the small number of infants born with such severe disabilities that doctors can see they have extreme pain and no hope for life. Our estimate is that it will not be used but 10 to 15 times a year.”

A parent’s role is limited under the protocol. While experts and critics familiar with the policy said a parent’s wishes to let a child live or die naturally most likely would be considered, they note that the decision must rest with doctors.

The protocol was written by hospital doctors and officials, with help from Dutch prosecutors. It is being studied by lawmakers as potential law.

Under the protocol, assisted infant deaths are investigated, but so far all of them have been determined to have been in the patients’ best interests.

Euthanasia has been legal in the Netherlands since 1994. Under the law, any critically ill patient over age 12 can request an assisted death, including adults in the early stages of dementia.

Opponents of expanding euthanasia to younger children cite a recent Dutch court ruling against punishment for a doctor who injected fatal drugs into an elderly woman after she told him she didn’t want to die. The court determined that he’d made “an error of judgment,” but had acted “honorably and according to conscience.”

News reports say that since that decision, some elderly hospital patients have been carrying written appeals not to be euthanized. What happens to vulnerable people is a particularly sharp issue in a continent where birthrates have declined and populations have aged. Euthanasia opponents say that as costs increase for long-term care, financial reasons could creep into euthanasia debates.

“The danger, of course, is ensuring a debate on the right to die does not become one on a duty to die,” said Urban Wiesing, the chairman for ethics in medicine at Germany’s prestigious Eberhard Karls Tuebingen University.

The issue is a particularly delicate one in Germany, where euthanasia was used by the Nazis as cover for wide-scale murders of disabled people, among others. Germany is one of the few countries where there is no serious push to legalize assisted suicide.

European advocates of expanding euthanasia laws say they’re acting in the best humanitarian tradition to halt intolerable suffering. Belgian Sens. Jeannine Leduc and Paul Wille noted that motive in their proposed law: “Their suffering is as great, the situation they face is as intolerable and inhumane.”

But others worry that after children, who will be next?

“I do accept that there are very difficult cases, very rare cases where a baby is in such pain that death would be the humane option,” Dutch ethicist Jochemsen said. “But hard cases make bad laws. As soon as a law is passed, it will expand the number of those who are considered extreme cases.”