A Conservative MP is calling for a special committee to examine when human life begins, a call opponents say is an excuse to reopen the debate over abortion.

Stephen Woodworth, who represents the Ontario riding of Kitchener Centre, has filed a motion in the House of Commons to form the committee. Woodworth says Canadian law is based on a 400-year-old definition imported from Britain that says life is considered to start once a baby is born and no sooner.

Prime Minister Stephen Harper has repeatedly said he doesn't want to reopen the debate, but his backbench MPs have so far been free to raise the issue.

It's wrong to accept a law that says some human beings are not human beings, Woodworth argued Monday morning.

"This story has to do with one parliamentarian's belief that justice demands honest laws based on cogent evidence and principle," he said.

"It's simply not legitimate — not even to achieve some important or desired result — for Parliament to accept a law that says that some human beings are not human beings when they are. That's a misrepresentation that prevents us from even having an honest conversation about it."

Government says won't reopen debate

Justice Minister Rob Nicholson released a terse statement before Woodworth's news conference finished.

"Private member's motions are considered in accordance with the rules of Parliament," the two-line statement said. "The prime minister has been very clear [that] our government will not reopen this debate."

Woodworth has called for a debate on the issue in the past and says it's separate from the debate over abortion.

"They do intersect but there are many questions which are not common to them both," he said.

"Once we decide whether or not a child is a human being before birth, then we can have an honest conversation about all of the other issues."

Responding to a 2008 election survey by Campaign Life Coalition, an anti-abortion group, Woodworth said he believes life begins at conception and sees no circumstances under which abortions should be performed.

No legal restrictions on abortion

Canada has had no legal restrictions on abortion since 1988, when the Supreme Court struck down a law limiting the procedure. The Canadian Medical Association issues guidelines on abortion that consider the viability of the fetus. The CMA says its position is that there is no need to replace the law struck down in 1988.

Opposition MPs say it's clear Woodworth is trying to reopen the debate.

Interim NDP Leader Nycole Turmel said the discussion over when human life begins is very close to the debate on abortion.

"It was dealt with years ago, the right of women to control her body."

Turmel said Harper should instruct Woodworth to withdraw the motion if has control of his caucus and is serious about not wanting to reopen the abortion debate.

Interim Liberal Leader Bob Rae said Woodworth is effectively starting up the abortion debate.

"When [the motion] comes for a debate, there will be a debate, clearly, on the question of abortion," he said. "But each member of the chamber has the right to bring private initiatives."

"I think there is a good majority of the chamber who won't vote for it."

Woodworth expects his motion to get an hour of debate in March and another hour in June.

It's not clear whether the motion would pass. The NDP, Liberals and Bloc are likely to vote against it. But while private members' business is usually given free votes, Harper could whip his cabinet members, forcing them to vote against it and likely denying the motion enough support to pass.

Abortion has come up twice in the past year, including during the last federal election campaign when Saskatoon MP Brad Trost told an anti-abortion group that the government was denying funding to the International Planned Parenthood Federation due to their lobbying efforts.

It arose again when International Co-operation Minister Bev Oda approved funding for the federation. Trost and fellow Saskatchewan Conservative MP Maurice Vellacott spoke out against the decision.