PARIS (REUTERS) - Several hundred thousand people are expected to march through Paris on Sunday against the planned legalisation of same-sex marriage in the first mass protest against the unpopular President Francois Hollande.

Strongly backed by the Catholic hierarchy, lay activists have mobilised a hybrid coalition of church-going families, political conservatives, Muslims, evangelicals and even homosexuals opposed to gay marriage for the show of force.

So many are expected to converge on Paris from around France that police had organisers split it into three separate columns starting from different points around the city and meeting in the Champ de Mars park at the Eiffel Tower.

Frigide Barjot, an eccentric comedian leading the so-called"Demo for All," insists the protest is pro-marriage rather than anti-gay and has banned all but its approved banners saying a child needs a father and a mother to develop properly. "We're all born of a man and a woman, but the law will say the opposite tomorrow," she said last week. "It will say a child is born of a man and a man."

Mr Hollande, who promised to legalise gay marriage and adoption during his election campaign last spring, has a comfortable parliamentary majority to pass the law by June as planned.

But his clumsy handling of other promises, such as a 75 per cent tax on the rich that was ruled unconstitutional or his faltering struggle against rising unemployment, has soured the public mood. A mass street protest can hardly help his image.

Same-sex nuptials are already legal in 11 countries including Belgium, Portugal, Netherlands, Spain, Sweden, Norway and South Africa, as well as nine US states and Washington D.C.

Gay marriage opponents such as Cardinal Andre Vingt-Trois, head of the Catholic Church in France, have asked why Hollande is pushing through a divisive social reform called "marriage for all" when voters seem more concerned about "jobs for all." Vingt-Trois spearheaded the opposition with a critical sermon in August. Other faith leaders - Muslim, Jewish, Protestant and Orthodox Christian - soon spoke out too.

Avoiding religious arguments that could put off the secular French, they struck a chord with voters by stressing problems they saw emerging from same-sex marriage rather than letting the government shape the debate as an issue of equal rights only.

Opinion polls show reform zeal cooled somewhat once these arguments were heard. Support for gay nuptials has slipped about 10 points to under 55 per cent and fewer than half the French now want gays to have adoption rights.

Under this pressure, legislators dropped a plan to amend the draft law to allow lesbians access to assisted reproduction techniques such as artificial insemination that are now limited to heterosexual couples with fertility problems.

Organisers insist they are not against gays and lesbians, but for traditional marriage. "We are marriagophile, not homophobe," said Barjot, author of a book entitled Confessions Of A Trendy Catholic. Most national faith leaders will not join the protest, but at least eight Catholic bishops have said they would march.

"I'm happy many Catholics will be mobilised, but this is not a church demonstration against the government," said Vingt-Trois, who plans to go meet marchers but not join them.

Opposition leader Jean-Francois Cope and other conservatives, as well as leaders from the far-right National Front, will march as private citizens without political banners.

Civitas, a far-right Catholic group whose protests have been openly anti-gay, plans a rival march that will run parallel to one of the "Demo for All" columns. Organisers say they will have about 10,000 volunteer marshals to keep order during the march.