Electric shock therapy for mentally ill children will continue to be allowed in NSW, after a review of the state's Mental Health Act stopped short of banning the treatment.

Instead, it is believed the act will be amended to make it mandatory for a specialist child and adolescent psychiatrist to assess patients aged 16 and younger, and each individual case to be signed off by the Mental Health Review Tribunal, before electro-convulsive therapy (ECT).

The draft legislation to amend the Mental Health Act is due to go to cabinet shortly for consideration and then will be publicly released. It comes as the Victorian government has resisted pressure to ban ECT for those under 13.

Of the 750 people who were treated with ECT in NSW mental health units last year, four were minors, aged 16 or 17, according to NSW Health. ECT is used to treat mental illnesses such as depression, bipolar or schizophrenia only after other treatments have failed.

Advocates for mentally ill children argue there needs to be more research into the risks and benefits of ECT for those under 18.

''We're worried about the impact on a child's brain development. I wouldn't have ECT on kids until more was known about it,'' Dr Peri O'Shea, the chief executive of the NSW Consumer Advisory Group - Mental Health, said.

But University of Sydney professor of child and adolescent psychiatry, Garry Walter, said there was no evidence ECT adversely affected brain development in young people.

''Ethically, how can one justify depriving a young person of a treatment which is safe and potentially life-saving?'' he said.