As Belgium's euthanasia laws come under scrutiny over the death of a woman with autism, one physician admits he has personally ended the lives of around 140 people.

Despite the staggering death toll, Dr Marc Van Hoey told the Daily Mail it is 'never easy' to end a person's life.

'That would make me sound like a terrible sadist. It is an act of pity. An act of empathy,' he said.

The 57-year-old, who is based in Antwerp, told the newspaper that the people he has euthanised include a good friend of more than 15 years after she had a stroke, a 34-year-old woman with chronic depression, and another friend who was suffering from pancreatic cancer.

'He was really suffering badly,' he said.

While Dr Van Hoey is unapologetic about helping people to end their lives, he is facing the possibility of prison as the Belgian authorities investigate the 2015 euthanisation of an elderly woman who was struggling to come to terms with the sudden death of her daughter.

'It is like the Sword of Damocles hanging over me,' he said. 'It's very worrying but my conscience is clear.'

The case has yet to go to court but while the investigation continues, Dr Van Hoey is not allowed to participate in any more mercy killings.

For another three doctors practising euthanasia in Belgium, the authorities have already moved ahead with criminal charges.

The doctors from East Flanders are to stand trial on suspicion of poisoning Tine Nys, a 38-year-old woman who was diagnosed with autism two months before her assisted suicide.

News of the prosecutions has been welcomed by Brother Rene Stockman, the head of a Catholic order that runs psychiatric homes in Belgium, saying euthanasia in the country was 'uncontrolled'.

'We all know that Belgium is on the top with a very liberal law on euthanasia, even for minors and psychiatric patients,' he said.

'We can only hope that this case will invite people to reflect which way they are going with society, where absolute freedom and autonomy and self-determination have become absolute number one on the scale of values.'

Belgium has some of the most liberal euthanasia laws anywhere in the world, allowing children of any age to request assisted suicide as long as they are deemed to have the mental capacity to do so and the consent of their parents.