A child euthanasia debate has divided Belgian parliamentarians ahead of Thursday's vote expected to legalise the right to grant euthanasia for terminally ill children.

The law will make Belgium the first country in the world to remove the age limit for the procedure.

The lower house of parliament is set to back the law with a majority after what is almost a universal taboo was broken last December when the country's Senate approved it by a 50-17 vote.

In Belgium, a child seeking euthanasia would need to be assessed by a psychologist, a requirement that would effectively rule out the very young. Parents would also have to approve their child's decision.

Backers of the vote believe the new law is necessary to provide a legal framework to requests, but opponents said a child is unable to decide on life and death, and fear for a slippery slope or even wider interpretations.

Socialist Karine Lalieux said the law would not force anyone to opt for euthanasia but rather give those who want a merciful end to suffering the right to do so within a legal framework.

“It's not a matter of saying there are good and bad countries, good and bad parents, some are pro-life, some are pro-death.

“It's about extremely complex situations and here we try to provide a framework for situations that actually exist in practise.”

Neighbouring Holland already allows euthanasia for children as young as 12 years, although only five cases have been recorded since 2002, only one of them under 16.

Belgium would go further by removing any reference in its law to the age of the child.

The Belgian law instead would require a psychologist evaluate the child's ability to choose to die. But opponents said it is impossible to determine whether a child is able to take such a decision.

Belgium is already one of the world's most liberal countries when it comes to euthanasia, making it available to adults who are not terminally ill.

The country's rules on euthanasia came under international scrutiny last year after the case of deaf twin brothers who were about to turn blind were granted the right to die.

Also in the case of a transgender person given the right to die after an unsuccessful sex change operation.

The new law does state children seeking euthanasia would have to be terminally ill.