A fierce backlash against Belgium's right-to-die law has been prompted by an increase in the number of people requesting euthanasia on the basis of depression.

Belgian bishops have praised a call to revise euthanasia laws that are widely deemed too loose. A group of 65 medical professionals, ethicists and philosophers published a letter in Flemish newspaper De Morgen earlier this month, urging legislation to be altered to remove the option for euthanasia purely on the basis of psychological suffering.

The letter said: "As representatives of the various directly-involved professional groups, from different parts of the country and from across the different ideological fault lines, we are alarmed by the increasing trivialisation of euthanasia on the grounds of mental suffering alone."

The current law in Belgium "assumes wrongly that there are objective clinical criteria for psychological suffering that might justify euthanasia," the letter continued, and therefore "euthanasia on the grounds of mental suffering alone cannot be regulated by law."

Carine Brochier, project manager at the Belgium-based European Institute for Bioethics (EIB), told Christian Today that the original meaning of the Belgian law has been interpreted differently by different doctors. Legislation dictates that a patient can only be euthanised in the final stages of his/her suffering if their medical situation "causes constant and unbearable physical or psychological suffering which cannot be alleviated and is caused by a life‐threatening and incurable accidental or pathological illness".

Anti-euthanasia campaigners say this means that a patient can request to be euthanised on the basis of psychological suffering if, and only if, it is as a result of a pathological illness. If a patient says he is suffering from psychological unbearable pain, it should be the result or consequence of his physical medical situation.

However, a number of people have been euthanised on the basis of suffering "heavy depression" with no links to a physical illness, Brochier said, as the law has been interpreted differently by some doctors and by the Evaluation Commission.

Euthanasia has been legal in Belgium since 2002, but the country has received significant criticism from faith and human rights groups who say legislative safeguards are too weak. It is feared that vulnerable people could be coerced, and that those suffering from psychological illnesses, such as depression, are having requests to be euthanised accepted by doctors, despite the impossibility of proving that they are incurable.

Speaking to Catholic News Service on Friday, spokesman for Belgium's Catholic bishops, Father Tommy Scholtes, said, "we're always opposed to euthanasia" and offered the bishops' support in the fight to change the law.

"Although the Church holds no position on the scientific arguments around euthanasia, we can see these medical practitioners have explained them effectively here," he said of the December 8 letter.

"Although strong suffering can be very difficult to bear, palliative care will always offer a better answer."

Belgian MP Els Van Hoof of the Christian Democrat Party also stated her disapproval of Belgium's law, saying it is clear there are "serious gaps [in the law], particularly with regard to the 'safety valves' that are built to prevent abuses".

The EIB has dedicated years to researching the effect of legalised euthanasia. A 2012 report concluded that euthanasia is "trivialised" in Belgium, finding that the number of reported cases of euthanasia rose by 89 per cent between 2010 and 2013 – from 953 to 1,807.

In 2013, 67 people were euthanised on the basis of psychological suffering alone. The case of Belgian serial rapist and murderer Frank Van Den Bleeken made headlines last year after he won the right to die citing "unbearable psychological anguish" as a result of his uncontrollable violent sexual urges. However, the euthanasia procedure was later cancelled, and he was moved to a psychiatric prison ward.

An increase in people with depression asking to be euthanised isn't necessarily a sign of the medical system in Belgium failing, Brochier said, but a symptom of the failure of society as a whole.

"If you look at the reason for depression, you will see that it is because people feel alone and they don't see the meaning of life any more. A second cause of depression is unemployment. But are we going to solve our unemployment crisis and our loneliness crisis by allowing euthanasia? That would be a real problem."

Brochier said she feared that "more and more" people suffering from depression would request to be euthanised in Belgium as the procedure is normalised. There is a cultural pressure to accept euthanasia as the compassionate response to illness, she said.

"It is a real danger," she added. "I would guess that people with depression will feel more and more inclined to ask for euthanasia, which would be a dramatic problem."

According to Brochier, it is becoming "very fashionable" to request euthanasia.

"It is presented by the media as the best way to die," she said. "You are in control of your life, you don't want to depend on other people or be alone, you're tired of living, so it's the best way to get out of this life. And we can understand that. But as I feel it and see it more and more, euthanasia is not just the problem of one person, euthanasia is an epidemic problem.

"It is because we leave people alone, we are so individualistic."

To say euthanasia is the compassionate response to suffering "is a lie", Brochier said.

"Compassion is not killing. Compassion is to work at the side of the person, and suffer with him or her, but not put an end to their life; that's a false compassion."

Instead, we need to invest in the lives of vulnerable people, she continued. "Euthanasia is killing each one of us but we don't realise it.

"It is like a stone falling in the water – at the point of impact, it makes ripples. Euthanasia is exactly the same, but we don't see and we don't want to understand the impact it is having on our country."