A professor says that legalising euthanasia has been devastating on the elderly, poor and disabled.

Otago University doctors have reviewed the laws, practices and modifications in countries where it's been introduced.

Old Age Psychiatry associate professor Yoram Barak says our public debate isn't well informed.

He's calling on psychiatrists to say 'no' to euthanasia.

"The long and short of it is anywhere from 70 to 75 per cent of people who are actually killed, so called euthanised, in countries where it is legal are the elderly and  the poor." 

Barak says the debate centres on choice, rights and dignity, but euthanasia becomes discriminatory. 

He says ignoring history means we'd be killing people without options. 

"When we talk to the elderly and the poor about why they wish to be killed or euthanised, they say they have become a burden on their families and on society, so it is really a choice." 

He says the Dutch government's considering extending euthanasia to anyone over 70 years old who feel they've fulfilled their role in life.

The research found that suicide rates have increased between five and 15-percent in countries where euthanasia is legal.

Barak says it's a contradictory message. 

"Once the message out there is that some lives are not worth living, then the next steps would be that suicide is fine."

New Zealand's End of Life Choice Bill has passed its second reading and is in final committee stages.