Thousands of demonstrators gathered on Parliament Hill Thursday for the annual March for Life anti-abortion protest, as the Conservatives repeated that they won't reopen the issue.

Gordon O'Connor, the government whip and the person who ensures MPs toe the party line, says people have a right to express themselves, but Stephen Harper's government won't reopen the abortion debate.

"Our government has said, since [2005], we will not bring in any abortion laws. Period. No matter pro, against, whatever, no abortion laws," O'Connor said.

O'Connor spoke against a motion by Conservative MP Stephen Woodworth two weeks ago. The motion calls for a special committee to study the section of the Criminal Code that defines human life.

Those who spoke at the demonstration countered Harper's past statements that his government won't touch the issue.

"You have heard it said that the debate over the protection of the unborn is over. I say look at this crowd," said Bruce Clemenger, president of the Evangelical Fellowship of Canada.

"We cannot afford not to have the conversation. I say Parliament needs to catch up with what Canadians believe."

The RCMP estimated there were 10,000 people at the protest. A spokesman for Campaign Life Coalition, which organizes the march, said they counted 19,500 people.

Protesters from across Ontario joined the rally, including busloads of teens from church organizations and schools.

Delroy Dyer, a 23-year-old student at Carleton University, said he opposes abortion because he's in favour of personal liberty.

"The beginning of that is life," he said.

'Her body, her choice'

About 150 to 200 pro-choice protesters also gathered on the side of the anti-abortion protest. Women in the pro-choice group chanted, "My body, my choice," while men replied, "Her body, her choice."

The pro-choice side made a point of noting there were few women speaking against abortion. Most of the speakers addressing the crowd were men, including several MPs.

Polly Leonard, who carried a megaphone and helped lead the pro-choice group in chants, said women will find other ways to end pregnancies if they don't have legal means.

"Life happens and you need to be able to do it safely, legally and [have it] accessible," she said.

Standing nearby, Josh DeVouge and Bill Berkhout said they don't think anyone else should have a say in what women do with their bodies.

"Giving that kind of life-changing option, into the hands of someone else, be it the family, government or even the father of the child, it's nobody's right to take that right away from someone else," Berkhout said.

"I'm not pro-abortion. I'm pro-choice."

MPs debated Woodworth's motion for an hour last month. It will return to the floor of the House for another hour of debate and a vote in June or September. The motion is not binding.