Prime Minister Stephen Harper said he will respect today's vote against revisiting debate on same-sex marriage, and considers the matter closed.

MPs voted 175-123 on Thursday against a Conservative motion calling for the government to introduce legislation restoring the traditional definition of marriage.

"We made a promise to have a free vote on this issue, we kept that promise, and obviously the vote was decisive and obviously we'll accept the democratic result of the people's representatives," said Harper. "I don't see reopening this question in the future."

Conservative House Leader Rob Nicholson said he was disappointed with the result of the vote, but that it was still a healthy exercise in democracy.

"I support the traditional definition of marriage and I always have," he said.

He also said the government has "no plans" to introduce a defence of religions act, to protect religious institutions from being forced to marry same-sex couples.

Critics say such an act would be redundant since those rights are already protected under the Charter of Rights of Freedoms.

CTV's Ottawa Bureau Chief Robert Fife said Harper knew Thursday's motion wouldn't pass.

"In fact, the resolution -- even if it did pass -- would have had no force of law," he said.

"If Mr. Harper was serious about outlawing same-sex marriage, he would have put in a resolution to invoke the notwithstanding clause to override the Charter of Rights and Freedoms, and he wasn't willing to pay that political price."

New Democratic MP Bill Siksay told CTV's Mike Duffy Live he's glad the debate is finally over.

"As a gay man, I'm getting tired of constantly having to debate whether or not I'm an equal participant in Canadian society," he said.

"This debate has lasted 32 years, when you consider the first time a gay couple tried to get a marriage license in Canada. That's a long time to be working on this."

Most Tories voted in favour of Thursday's motion, along with 13 Liberals. Another 13 Conservatives voted against it, joining all present NDP and Bloc Quebecois MPs, and the majority of Liberals.

Conservatives who opposed the motion included Foreign Affairs Minister Peter MacKay, Indian Affairs Minister Jim Prentice and James Moore.

Liberals who voted in favour of the motion included Dan McTeague and John McKay, who had urged Liberal Leader Stephane Dion to allow a free vote.

The Conservative government motion called on the government ''to introduce legislation to restore the traditional definition of marriage without affecting civil unions and while respecting existing same-sex marriages.''

Canada was the fourth country, after the Netherlands, Belgium and Spain, to legalize homosexual marriage.

In 2005, MPs passed a law legalizing same-sex unions in the wake of court rulings that said barring gay couples from marriage was unconstitutional.

More than 12,000 gay couples across Canada have already wed.

The vote was held one day after MPs debated the divisive motion late into the night.

Nicholson launched Wednesday's debate in defence of his government's position.

"This is completely consistent with what we told the Canadian people we would do," he said. "We're fulfilling that promise."

Former Liberal cabinet minister Bill Graham dismissed the motion as a shoddy ''smoke screen" meant to sow political division.

''It's a manoeuvre designed to divide the House and the nation on an issue that's been decided.''

Graham said the only way for the government to restore the traditional definition is to use the Constitution's notwithstanding clause, which allows governments to override the Charter. Harper has said he would not do that.

Both Harper and Dion had said they would allow their MPs to vote their conscience.

Dion didn't support reopening the divisive debate, but he was concerned that imposing party discipline would hand the Conservatives more leverage on the issue.

Last year, 32 Liberal MPs voted against the same-sex marriage law.