Stirred-up supporters of the End of Life Choice bill have confronted the Whangārei National MP Shane Reti today over his refusal to support the legislation.

About 30 people, mostly senior citizens, challenged Dr Reti outside his office this afternoon, waving banners and demanding the right to assisted dying for those who want it.

Police watched on as the MP defended his views, amid some robust exchanges.

Whangārei emergency specialist Gary Payinda told the MP palliative care had its limits.

"If you had a dog dying of bone cancer, incontinent; in pain and the vet can't relieve the pain, the vet has the option of relieving intractable, unrelenting suffering.

"No one would condemn that. If we can do that for an animal, why can't we do that for a loved one?" Dr Payinda said.

Dr Reti said the comparison was not valid.

"I believe it's unfair to compare the integrity of human life, and animal life. There are clear differences, in my view."

The Whangārei MP later told RNZ he would not vote for the bill because he had spent his career as a doctor nurturing and protecting life.

He had made those views public before the last two elections, he said.