National Party MP Simon O'Connor has been backed by Labour and Green Party colleagues after his suitability to head an inquiry into euthanasia was questioned because of his personal beliefs.
Mr O'Connor is the chairman of Parliament's health committee, which is considering a petition to legalise euthanasia in New Zealand.
The devout Catholic, who once trained for the priesthood, is firmly opposed to assisted suicide.
Act Party leader David Seymour, who supports a law change, said Mr O'Connor had been too partisan on the issue and should step down as chairman.
Mr Seymour blamed Mr O'Connor for the committee's terms of reference, which he said had placed too much emphasis on suicide.
"That is very different from assisted dying," he said.
The National MP had also solicited submissions on the inquiry in an interview with a Catholic newspaper, putting an emphasis on opposing submissions.
In a blog post on the website The Spinoff, entrepreneur Gareth Morgan also questioned whether Mr O'Connor was fit to lead the inquiry, pointing to his speech at an event hosted by hardline anti-euthanasia group Right to Life New Zealand.
Yesterday, Mr O'Connor rejected calls to step aside and said the outcome of the inquiry was not a foregone conclusion. "I can hold a personal view but also run a committee in a way that is ... professional."
The petition's sponsor, former Labour MP Maryan Street, had submitted her petition with the full knowledge any inquiry would be led by him, he said.
Asked about the inquiry's terms of reference, Mr O'Connor said the nine-person committee had a robust debate on them, but they were approved unanimously. It is understood that at least two committee members felt the terms of reference should have been framed differently. Labour MP Louisa Wall said the terms were "not ideal", but she would not comment further.
Green MP Kevin Hague said the terms placed too much emphasis on suicide and he believed Mr O'Connor went too far as a committee chair by soliciting submissions. But he had no concerns about his impartiality.
Labour deputy leader and health spokeswoman Annette King said Mr O'Connor was "scrupulously fair".