If Canadians thought the last House of Commons debate around abortion was contentious, the next one is shaping up to be even more complicated and potentially a closer vote.

British Columbia Conservative MP Mark Warawa is promoting a private member's motion that calls on the Commons to condemn the practice of sex selection. Sex selection occurs when a woman aborts a fetus -- usually a female fetus -- after determining the gender through an ultrasound.

Warawa said Wednesday his motion is about discrimination against women, rather than about reproductive rights. It is not likely to come up for debate until March.

The father of two girls said he was compelled to act after watching a CBC investigative story last June about 3-D ultrasound clinics revealing the sex of babies to women early enough for them to receive an elective abortion. He doesn't have numbers on the prevalence in Canada.

"I think parliamentarians are faced with two choices: We either condemn this form of discrimination against women and girls or we endorse it," Warawa said accompanied by 11 Tory colleagues, most of them vocal members of the party's pro-life caucus.

"It's not something you can ride the fence on."

Although Warawa and his supporters would not concede a connection between the motion and the wider debate over restricting abortions, the prime minister's office is doing just that.

"The government is opposed to opening this debate. Parliament has already voted on this issue," spokesman Carl Vallee said in response to a question about the Warawa motion.

"We don't think it should be opened again."

Despite Harper's unequivocal stand on the issue, related motions continue to pop up. Conservative MPs present a constant stream of petitions in the Commons to limit abortion rights or change legislation.

The last time the Commons dealt with the issue of abortion was in September, when Ontario Conservative Stephen Woodworth unsuccessfully asked that a committee be struck to examine when a fetus is considered a child under the Criminal Code.

But asking MPs to condemn a practice that specifically targets a particular gender might not be as easy for some to reject -- especially Conservatives.

Status of Women Minister Rona Ambrose surprised many when she voted in favour of Woodworth's motion, explaining that she was concerned about sex selection.

Already, the NDP and Liberal leaders are saying they will not support the motion, calling it a thinly veiled attempt to reopen the debate on abortion.

NDP Leader Tom Mulcair noted that the Warawa brought forward his motion the same week Woodworth's died in the Commons.

"Of course these are complicated issues, there's no denying that, but we know what it's really about," Mulcair said.

"It's Stephen Harper and his Reform party base trying to reopen the abortion debate. We're not going to be fooled by it."

Labour Minister Lisa Raitt, who voted against Woodworth's motion, hinted at some weariness with such motions.

"I'm pretty sure we've dealt with all these issues before. I mean, we've done this," said Raitt.