Lesley Martin served more than seven months in jail

Ms Martin was jailed in April for injecting her terminally ill mother with a morphine overdose. The 69-year-old died the next day.

Ms Martin's case sparked a fierce debate on the ethics of mercy killing.

After her release on Monday, she said she would continue to campaign for legislation on euthanasia.

She said she had no regrets about the stance she took, and added that her time in jail was "part of bringing more awareness to the whole issue of VE [voluntary euthanasia] in New Zealand".

What Lesley's been going through... is a stark reminder to us that the law on this issue is uncompromising and really needs to change Dr Philip Nitschke, Australian mercy killing campaigner

Lesley Martin is one of New Zealand's leading pro-euthanasia campaigners.

She helped found Exit New Zealand, a voluntary euthanasia lobby group with links to Exit Australia, the group founded by Australian mercy killing campaigner Dr Philip Nitschke.

Dr Nitschke was waiting with Ms Martin's family to greet her as she left Arohata Women's Prison on Monday.

"What Lesley's been going through has been watched by people all over the world... and it's a stark reminder to us that the law on this issue is uncompromising and really needs to change," Mr Nitschke told New Zealand Radio.