Abortion rights are at the centre of a debate set for this afternoon as MPs consider whether to hold a special committee to look at when human life begins.

Stephen Woodworth, a Conservative MP from Kitchener, Ont., introduced a private member's motion calling for the committee. Woodworth says current Canadian law says human life begins when a child has fully emerged from the mother's birth canal, which is based on a 400-year-old definition imported from Britain.

The motion isn't binding, but allows MPs to spend two hours discussing the need — or lack thereof — for a committee to examine the question of when life begins.

When he announced the motion, Woodworth had argued he was simply interested in updating the law to agree with 21st-century medicine. But speaking to Radio-Canada on Monday, he admitted his motion is linked to abortion.

"It certainly allows us to have an honest discussion about the abortion question. How can we honestly discuss all of the complicated issues around abortion if we cannot decide whether or not a child is a human being before the moment of the complete birth?" Woodworth said.

Speaking to reporters Wednesday, he cast the debate as one about human rights.

"If in Canada we cannot agree that a law which decrees that some human beings are not human is wrong, then we need to definitely have some discussion about that. That really is the starting point for any just system of laws," Woodworth said.

"It’s a serious debate. It should be addressed."

The motion will get one hour of debate at about 5:30 p.m. ET. Then it drops to the bottom on the order of precedence, and gets another hour of debate when it returns to the top of the list. The House will vote on the motion the following Wednesday, which Woodworth expects will be in June or September, after the summer recess.

No New Democratic MP support

NDP Leader Tom Mulcair said no one in his caucus supports the motion but he plans to whip the vote, or force his MPs to vote along party lines.

"We're resolutely in favour of women's right to choose, so it's very clear for us, and we are absolutely opposed to this motion of Mr. Woodworth," he said.

Interim Liberal Leader Bob Rae said he's going to allow Liberal MPs to vote however they want, known as "voting their conscience."

In question period, New Democrat MP Niki Ashton said the Conservatives are rolling back Canadian women’s rights.

"A woman’s right to choose, in Canada, in 2012, is not up to negotiation," she said.

But some of Woodworth's colleagues disagreed.

Conservative Saskatchewan MP Brad Trost, who has previously talked about wanting to limit abortion, said he plans to support the motion.

Trost said MPs keep bringing up the issue — despite Prime Minister Stephen Harper saying repeatedly that his government will not reopen the debate on abortion — "because Members of Parliament are duty-bound by both their constituents and their conscience to argue for things that they feel [are] important."

"Mr. Woodworth feels this is important. He feels this is a thoughtful, proper thing for Canada. And I, like a lot of members, think it’s time that we looked at this in a way that brings compassion to everyone involved."

Question of conscience

While Harper has pledged not to raise the abortion issue, it's not clear whether the Conservatives will whip the vote for cabinet ministers or for the caucus as a whole.

Immigration Minister Jason Kenney, who is a practising Catholic, says party tradition is to allow free votes on issues of conscience.

"I'm going to consult my constituents and consider the implications before taking a decision," Kenney said.

"My position is that we must have free votes on questions of conscience."

A spokesman for Harper says the government doesn't usually "communicate its parliamentary strategy" before a vote.

"The [prime minister] has been clear — he will not reopen this issue," Andrew MacDougall told CBC News.