Prime Minister Stephen Harper said Thursday he will vote against a motion tabled by a Conservative MP to have Parliament determine when human life begins.

The private member's motion was launched by Kitchener, Ont., MP Stephen Woodworth, who contends the current legal definition of human life is based on 400-year-old British tradition and needs to be updated.

The motion asks that a special committee of the House of Commons be established to review the issue of when exactly human life begins.

During a debate Thursday, Government Whip Gordon O'Connor said the motion's "intention is to restrict abortion in Canada," and he added that the "government will not reopen the debate."

Some Liberal and NDP MPs said Woodworth's goal was to ultimately criminalize abortion.

"Make no mistake about it, this is a full frontal assault on women's fundamental right to choose," said NDP Gatineau MP Françoise Boivin.

Prime Minister Stephen Harper has frequently said he does not want to reopen the debate on abortion.

During question period earlier in the day, he responded to NDP Leader Thomas Mulcair who asked "why he allowed his Conservative MPs to reopen the debate."

"Every private member can table bills and motions in this House," Harper responded. "Party leaders don't have any control over that. This motion was deemed votable by an all-party committee of the house. I think that's unfortunate. In my case I will be voting against the motion."

Woodworth takes issue with Section 223 of Canada's Criminal Code, which states that human life begins when a child emerges from its mother's body.

"When the rights of two people conflict it is never acceptable to deny that one of them is a human being deserving recognition as a human being," Woodworth said during the debate.

However, he suggested that abortion laws would not necessarily be affected by the findings of a committee were it to be formed.

"Do you need to pretend a child is not human until the moment of complete birth in order to justify abortion? You do not," he said. "Even if a child is found to be a human being, it is arguable that the mother's rights will outweigh the child's rights."

Abortion rights advocate Carolyn Egan told CTV that the rules around the procedure are quite clear in Canada and the Canadian Medical Association has regulations in place to guide physicians.

"I think we've seen actually the rate of abortion going down over the last number of years because of more information and education on birth control, so I don't think it's an issue," said Egan, a spokeswoman for the Abortion Rights Coalition of Canada.

Even though science has advanced, the medical community supports a woman's right to abortion and the medical definition of a fetus is well established, Egan said.

"I think we have to look clearly at what's happening here, the intent is to re-open the abortion debate, but the intent in the long run is to outlaw abortion (and re-criminalize women and doctors)," she said.

Andrea Mrozek of the institute of Marriage and Family Canada said it's incorrect to assume abortion is a fundamental right.

Most Canadians aren't even aware the country doesn't have a law governing abortion, she said in the same interview.

"This is an opportunity for there to be more information and those who oppose me on this idea that abortion is not a right, have nothing to fear from the result," Mrozek said.

The motion just opens a discussion on the topic of when life begins and isn't a bill to legislate abortion laws, she said.

But Egan said that's just a smokescreen to push for the elimination of abortion in Canada.

"There is no doubt in our minds this is about abortion, whether a woman has a right to abortion and whether abortion should be provided in this country and let's not fool ourselves," she said.

According to Mulcair, NDP caucus members will vote unanimously against the motion. Interim Liberal Leader Bob Rae says caucus members will be allowed to vote according to their conscience. The Conservatives haven't said what directions will be given to their members.

The motion won't come up for a vote in the House until June, or possibly September, according to CTV's Mercedes Stephenson.