Members of Parliament have passed a divisive and contentious bill, putting Canada one step closer to becoming just the third country in the world to sanction same-sex marriage.

After years of debate, the House of Commons put Bill C-38 to a vote after its third and final reading late Tuesday night.

With the Liberals enjoying the support of almost all the Bloc Quebecois and NDP MPs, the legislation passed easily in a 158 to 133 vote.

Now, it will take Senate approval and royal assent to make Canada the third country in the world, after the Netherlands and Belgium, to officially recognize same-sex marriage.

"(This) is about the Charter of Rights,'' Prime Minister Paul Martin said before the vote was cast Tuesday.

"We are a nation of minorities. And in a nation of minorities, it is important that you don't cherry-pick rights. A right is a right and that is what this vote tonight is all about."

But in the final hours before the vote Tuesday, the legislation continued to divide Martin's Liberal minority.

In a surprise announcement, Ontario MP Joe Comuzzi said he had to leave his cabinet post and vote against the government on the issue.

When asked about his decision, Comuzzi told CTV's Canada AM the announcement may have been last-minute, but his mind was made up long ago -- in accordance with the wishes of his constituents.

"I confirmed it through town hall meetings," the former minister of state for economic development in northern Ontario said in an interview Wednesday.

"After I confirmed that was going to be the case, because I was in cabinet, I had to keep that secret until yesterday."

Backbench Liberal MPs were free to vote their conscience, but cabinet ministers were under orders to vote in favour of the bill.

About three dozen Liberal MPs voted against the legislation that legalizes same-sex civic marriages at public venues like city halls and courthouses. Religious groups still have the right of refusal to sanctify same-sex marriages.

MPs' approval of the law marks the culmination of a long and divisive debate, with fierce opposition coming from the official Opposition, religious groups, and even members of the government's own ranks.

But the arguments appear far from over.

"(This) is effectively exposing people of faith to persecution and prosecution," president of the Canada Family Action Coalition Charles McVety said in reaction to the vote Tuesday night.

"I want to make it very clear today that this is the beginning of the formal fight against the definition of marriage."

Conservative Leader Stephen Harper, meanwhile, is promising that he won't let the issue rest. He says he'll bring back the same-sex marriage law for another vote if he becomes prime minister.

"There will be a chance to revisit this in a future Parliament," Harper said. "Our intention is to have a free vote."

He also repeated his claim that the law lacks legitimacy because it passed with the support of the separatist Bloc party.

"I don't think Canadians are going to accept as a final word a decision taken by only a minority of federalist MPs," he said. But Harper didn't specify how he would address the issue if the Tories were to form the next government.

Liberal Justice Minister Irwin Cotler said Harper is going to have to come clean and acknowledge that he would have to invoke the Constitution's notwithstanding clause to override the new law.

"They're going to have to acknowledge that they want to override the (Charter of Rights); override constitutional-law decisions in nine jurisdictions in this country; override a unanimous decision of the Supreme Court of Canada; override the rule of law in this country," Cotler said.

The clause is available to provinces to override federal laws that intrude on provincial jurisdiction.

But almost every provincial and territorial government has legalized same-sex marriage; and the new legislation will ensure that four "hold-out" jurisdictions -- Alberta, Prince Edward Island, Nunavut and the Northwest Territories -- must now strike down their traditional marriage laws.

"It's an historic moment, it's about equality for gays and lesbians," said NDP MP Libby Davies.

Alberta Premier Ralph Klein, who's "strongly opposed" to the bill on moral grounds, once threatened to invoke the Constitution's notwithstanding clause to maintain the traditional definition of marriage in his province.

In light of the vote, however, he acknowledged little can be done to stop same-sex marriages in his province now.

"Since this is federal legislation. To use the notwithstanding clause as contained in our own Marriage Act would be frivolous," Klein told reporters in Calgary. "It wouldn't stand up in any court of law. So there are some other options that we would have to consider."

Although some members of his caucus are threatening to use everything at their disposal to get around the legislation, Klein said "there are no legal weapons; there's nothing left in the arsenal."

After the same-sex vote was put to bed Tuesday night, the House immediately adjourned for the summer.

MPs won't meet again until Sept. 26.