The deep divisions within the Liberal government on plans to legalize gay marriage were laid bare Tuesday in the House of Commons when the Grits barely survived an Alliance motion to preserve the traditional definition of marriage.

The critical first test of the government's plan was passed by a razor-thin 137-132 vote.

The result could have been a dead heat, if not for NDP dissidents who did not attend and several backbench Liberals who switched votes at the last minute.

Tuesday's apparent deadlock now turns the explosive issue over to voters in next year's federal election, Alliance Leader Stephen Harper said.

"It's obvious now that this will be an issue in the next federal election," Harper said.

There is clearly much work to do on the issue within the Liberal caucus. Liberal MP John McKay, from Scarborough, Ont., supported the Alliance motion. He said the result of the free-vote needs to be kept in context.

"You've got to bear in mind that the cabinet was a whipped group in this vote," Mr. McKay told CTV after the vote. "There was heavy pressure on quite a number of MPs to vote the way the government saw things to be voted so, you know, how free that vote was is maybe a bit of a de-construction."

Mr. McKay said a number of his colleagues experienced intense pressure from cabinet ministers and regional groups to vote against the Alliance motion.

"I don't think that this is by any means finished," he said. "I think that this debate will play out and play out and play out some more - right into the next election. And I think that all of us will have to live with our votes, one way or another."

Svend Robinson, an NDP MP who strongly advocates same-sex marriage, voted against the Alliance motion.

"I have to say that it was far too close - it should have never been this close," Mr. Robinson said, blaming the Liberal schism on the issue flatly on Paul Martin. "Where has Paul Martin been on this issue of fundamental equality and respect for the Charter of Rights?" he said. "He's been totally invisible and it would never have been this close if Martin had shown some leadership."

Mr. Martin, who is widely expected to be the next Prime Minister, voted against the Alliance motion, declaring the national fabric strong enough to withstand the marriage debate.

Mr. Robinson said the vote was a signal for the government not to wait around for the court, but rather, to push same-sex marriage legislation through as quickly as possible.

"Move on it now - this is an issue of fundamental equality," Mr. Robinson said. "You've got a signal today from parliament that a majority of parliamentarians reject the use of the notwithstanding clause, that rejected an attempt to reaffirm the unconstitutional definition [of marriage]. I say, as [NDP Leader] Jack Layton has said today, bring it on.

The Alliance motion had no real power, but the Opposition hoped it would reveal the division amongst the Liberals on the issue of same-sex marriage.

In June, the Liberals introduced a bill that would allow such unions in Canada.

The Alliance motion Tuesday argued that the federal government's proposed bill is "an attack on religious beliefs" and a hypocritical move by the Liberals.

In 1999, a similar Alliance motion passed by a wide margin, 216-55. Prime Minister Jean Chrétien and Justice Minister Martin Cauchon both voted in favour of that motion, but now have changed their positions because they say times have changed and same-sex unions should be allowed.

The issue has caused a summer of heated debate and courts in three provinces — Ontario, Quebec and British Columbia — ruled in favour of gay marriages.

In his statement to the Commons earlier, Mr. Cauchon called on his fellow Liberal MPs not to support the motion because it could require the government to use the Constitution's notwithstanding clause to overrule the courts.

At the time of the 1999 vote, he said the Liberals weren't facing the "same clarity" in terms of a looming Supreme Court decision on the issue. Mr. Cauchon compared the changes in the same-sex marriage issue to the debate over giving women the right to vote.

With a report from the Canadian Press.