PARIS (Reuters) - Roman Catholic bishops and conservative politicians are stepping their campaign against French President Francois Hollande's plan to legalize gay marriage days before his government presents its draft law in cabinet.
Paris Cardinal Andre Vingt-Trois is expected to call for a broad mobilization against the law when Catholic bishops meet in the southwestern pilgrimage town of Lourdes for their annual plenary on Saturday.
Far-right National Front leader Marine Le Pen and Jean-Francois Cope, who is campaigning to lead the main opposition UMP party, both backed proposals this week for a large national protest march in defense of traditional marriage.
Protesters took to the streets of 75 cities and towns across France last week and lay Catholic leaders have called for another round of demonstrations in mid-November. Sample letters against the law have been posted on websites sent to elected officials.
"In a rare turn for France, the Catholic Church finds itself setting the tone for the political opposition," wrote the Catholic newspaper La Croix. "The bishops have been raising their voices in a crescendo."
The Socialist-led government will present its draft law on same-sex marriage in cabinet next Wednesday, following up on a campaign promise by Hollande last spring. It expects to submit the reform to a vote by mid-2013.
His government originally planned to rush through the change but rising opposition from Christian, Muslim and Jewish leaders slowed down the process.
French society is secular but religious leaders can still command respect, especially in rural areas. Some 62 percent of French identify themselves as Catholics but few attend church.
Faith leaders have avoided religious arguments and framed the debate as not one of gay rights but about the social and psychological changes the reform would make for families, especially for children of gay couples.
Surveys by the Ifop polling group show support for gay marriage has weakened from 65 percent in August to 61 percent now as the public debate has taken off.
Support for full adoption and assisted procreation rights for gay couples has slid from 53 per cent to 48 percent now.
Vingt-Trois, who launched the Catholic campaign in August with a national prayer day against same-sex marriage, on Tuesday urged political parties to let their deputies vote according to their consciences.
Le Pen said on Thursday she would join any national protest.
"This law could overturn the foundations of our civilization," she told Catholic media.
Mayors around the country have formed groups to pledge to preside at same-sex marriages if they are legalized or to demand a "conscience clause" to opt out of doing so.
The debate has heard some distinctly personal barbs.
"Isn't it a paradox that Francois Hollande, who was never in a hurry to slip a ring on anyone's finger, is rushing to legalize homosexual marriage?" asked UMP deputy Nadine Morano.
The president has four children from a long relationship with another Socialist politician, Segolene Royal, and now lives with a new partner, journalist Valerie Trierweiler.
Passing the law would make France the 12th country around the world to legalize same-sex marriage. It is already allowed in Argentina, Belgium, Canada, Denmark, Iceland, Netherlands, Norway, Portugal, South Africa, Spain, and Sweden.
Six states and the District of Columbia in the United States have legal gay marriage, as does Mexico City. Many countries have some form of civil union that grants gay couples most but not all of the rights of a traditional marriage.
France legalized civil unions in 1999 and they are now approaching the number of traditional marriages contracted annually. There were 200,000 "civil solidarity pacts" (PACS) against 250,000 marriages in 2010.
Originally seen as a kind of ersatz gay nuptials, the PACS has turned out to be "marriage lite" for heterosexuals, who make up 94 percent of all couples opting for this kind of union.
Reporting By Tom Heneghan; Editing by Angus MacSwan