A large American wartime poster proclaiming "We can do it" hangs behind the bar at Les Souffleurs, a fashionable bar in the Marais, the traditionally Jewish, but now gay, quarter of Paris.

The barman admits business is a little quiet for a Friday evening: the drinkers sitting on stools and chatting say they are concerned about the increasingly vocal and violent rise in homophobia in France, provoked by the bitter debate over same-sex marriage.

On Sunday the issue that has divided France will reach a potentially explosive peak as opponents of gay marriage take to the streets in a last-ditch attempt to stop the so-called "marriage for all" bill, which is expected to be approved by parliament finally on Tuesday. A demonstration by supporters of the right for homosexuals to marry and adopt children has also been planned.

Less than two weeks ago, in a spate of violence against gays, Dutch-born Wilfred de Bruijn was beaten up while walking arm in arm with his partner in Paris. De Bruijn posted a picture of his bruised and bloody face on Facebook, stating "it's the face of homophobia".

As an often ill-tempered debate in the national assembly came to an end last week, the violence was clearly escalating, with arrests at protests in the capital and other cities, and reports of attacks on gay bars.

Anti-gay marriage protesters, who have taken to calling their movement Le Printemps Français (the French spring, an echo of the Arab spring uprisings that overthrew unpopular dictators), mimicked the radical feminist movement FEMEN, whose members demonstrate topless, and took off their shirts outside the French parliament.

President François Hollande has condemned the "homophobic" violence, and his interior minister, Manuel Valls, has warned that the protests have been hijacked by far-right organisations.

The figurehead of the anti-gay marriage movement, the comedian Virginie Tellenne, who calls herself Frigide Barjot and who has described herself as "press attaché for Jesus", had earlier said: "If Hollande wants blood, he'll get it." She later retracted her comment, saying she had "gone too far".

However, she admitted "troublemakers" were joining protests and called on the government to round them up, saying they were "blackening" the organisation's image.

"On Sunday, many peaceful people will be in the streets and the forces of law and order have a responsibility to ensure calm demonstrations. We know the police have identified the troublemakers ... but they have done nothing," Tellenne said.

Back in Les Souffleurs, Dorothée Jenny, a 26-year-old bisexual working in human resources, said she had been incensed at the homophobia at a recent anti-gay marriage march. "I do think about it at the moment, but I don't want to change my habits. Hopefully, when the law is passed, things will calm down," she said. Her twin brother Hyppolite, a webmaster, agreed. "I wouldn't kiss my boyfriend in the street these days," he said. The pair thought those opposed to gay marriage were also using the demonstrations to rail against Hollande. "I'm surprised at the popularity of the anti-gay campaign. These are young people we could be talking with."

The twins' friend, Estelle Luporsi, 24, a bank worker, spoke of a climate of fear. "There are certainly areas in Paris where you have to pay attention," she said.

Standing at the bar, artist Daniel Vincent, 50, thought that the social media had exacerbated the violence and created a "paranoia of an invisible enemy" among the anti-gay marriage protesters. "It's very present on social media. It brings back a lot of the homophobic experiences [people] have had in the past, the old stories," he said.

"We're finding the same amalgamation of tensions that we had around the presidential elections," said his friend François-Henri Galland, a 41-year old teacher, pointing to when both right and left goaded each other on social networks.

In other bars in the Marais on Friday, after the parliamentary debate wound up, the gay community was out in force and determined not to feel under siege. Standing with a group of friends on the terrace of the popular Café Open, David Rol, a 40-year-old engineer, said he was more wary than afraid about going out in the Marais. "Scared no, because I come out in this area a lot, but tonight I thought there could be problems."

Jean Soubeyre, a 43-year-old who works in marketing, said the legitimacy given to homophobia in the current climate was horrible. "The law will pass, but it's crystallising all sorts of other problems, such as the financial crisis."

Rol agreed that the law will pass. "Hollande knows he doesn't have a choice. If he renounces it, he will lose all credibility," he said. "For me, the [anti-gay marriage] protests just confirm that France is a rightwing country at heart."