France's National Assembly on Saturday overwhelmingly approved the key article of legislation that will allow gay couples to get married and adopt children.
Deputies voted 249-97 in favour of Article One of the draft law, which redefines marriage as being a contract between two people rather than necessarily between a man and a woman.
Although the proposed law still faces at least another week of scrutiny before a final vote scheduled for February 12, it now looks set to emerge from parliament undelayed and undiluted.
After months of frenzied debate, the ease with which the law cleared its first major hurdle was welcomed by delighted gay rights activists.
"Things are going well and quickly, which is a relief for us," Nicolas Gougain of the Inter-LGBT lobby group told AFP.
"We've never seen so many deputies arguing the case for equality and for the recognition of different kinds of families. We can now look forward to the remainder of the debate calmly. It's fabulous!"
The article approved on Saturday was supported by deputies of the ruling Socialist Party, who enjoy an overall majority in the Assembly, other leftists and Greens as well as at least one member of the UMP, the main centre-right opposition force.
"We are happy and proud to have taken this first step," Justice Minister Christiane Taubira said. "We are going to establish the freedom for everyone to choose his or her partner for a future together."
But UMP deputy Philippe Gosselin said the government was forcing through legislation that France did not want.
"Today it is marriage and adoption. Tomorrow it will be medically assisted conception and surrogate mothers," he said in comments that reflected a widely felt concern among opponents of the government's plans.
The Archbishop of Paris, Andre Vingt-Trois, claimed on Saturday that moves to legalise surrogacy would logically follow the adoption of the legislation currently before parliament.
"What we predicted is already starting to happen," the cleric claimed, citing a government circular which recommends that the children of gay couples who have used the services of a surrogate mother outside of France should be granted French nationality.
Opinion polls suggest a clear majority of French voters support the right of gay couples to wed and a narrower majority favour them being granted the right to adopt as couples (gay men and women can already adopt as individuals if approved by social services).
Massive demonstrations across the country have underlined that those who oppose gay marriage feel very strongly about the issue and President Francois Hollande has been accused of pushing the legislation through without proper consultation.
The Catholic church has been heavily involved in mobilising opposition and protests were scheduled to take place again Saturday in towns and cities across France.
A national rally in Paris last month attracted hundreds of thousands of demonstrators and was at least twice as big as a protest staged by supporters of the reform.