English and his wife, Mary, are staunch Catholics. The PM says he's not interested in "liberalising" abortion laws.

Any review of abortion law is code for "liberalising it", says Prime Minister Bill English, and that's not going to happen on his watch.

The Abortion Advisory Committee is calling for an update of New Zealand's abortion laws, which are still part of the Crimes Act 1961.

But the committee's recommendations are unlikely to make any headway under a National government, as staunchly Catholic English says it's a "law that's stood the test of time".

CATRIN OWEN/FAIRFAX NZ Labour's Andrew Little and Jacinda Ardern would review abortion laws if in power.

English made the comments on TVNZ's Q+A on Sunday after being asked if he would consider a "modernisation" of the laws.

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"Well, I think what they mean is liberalise it, and we wouldn't do that," he fired back.

"But look, the Parliament has ways of working with this."

Labour leader Andrew Little and deputy Jacinda Ardern pointed out that while an issue like reviewing abortion law was a conscience vote, there was still room to review it, which would happen under a Labour government.

"[English] is deeply conservative on an issue like abortion. I happen to differ from him on that," Little told Q+A.

"I think that the advisory committee is right. The legislation has been around for the best part of 40 years. It does need to be reviewed and upgraded, and I agree with Jacinda - we should not have it in the Crimes Act; it is not a crime."

When abortions are still part of the Crimes Act, Ardern said it was "understandable" the committee would call for a review and "it would be timely".

While English said the Abortion Advisory Committee was welcome to have its opinion and recommendations, "they know what my opinion is".

English supports issues like abortion being dealt with through a conscience vote and, while his is only one of 121 votes, he says he'd hope others would vote with him.

Asked if his vote as Prime Minister held more weight and "set the tone" of how others voted, English said: "Well, look, if it does in that case, I'm quite happy that it sets the tone of not rushing into big changes in abortion law."

In the case of changes to euthanasia - David Seymour, leader of National Party support partner ACT, currently has a member's bill to legalise assisted dying - English said his position was clear.

"Well, my views about a range of social issues are pretty well known and fairly consistent in the Parliament, and if issues like, say, euthanasia arise, people will know where I stand on it and how I'll vote on it. That won't change," he said.

Little has been criticised by some for taking euthanasia off the party's agenda when he became leader and telling his MP Iain Lees-Galloway, who took over former MP Maryan Street's bill, to drop it from the ballot.

"I just did not regard it as a priority for Labour when we just had an election where we got 25 per cent of the vote. There were bigger priorities to deal with," Little said.

However, he does personally support euthanasia and backed Street's bill.