By Tom Heneghan, Religion Editor
PARIS (Reuters) - More than 100,000 protesters organized by Catholic groups staged separate demonstrations in French cities over the weekend to protest against government plans to legalize same-sex marriage next year.
Most of them took to the streets on Saturday, backed by the French Catholic Church and joined by several senior clerics, and several thousand more paraded with ultra-traditionalist Catholics in Paris on Sunday.
Though marching separately, they chanted the same slogan - "one father + one mother for all children" - and denounced the Socialist government's plan. Polls show about 60 percent support for the reform, but not the right for gay people to adopt children.
"Shame on the president, who'll protect the infants?" chanted protesters on Sunday as they passed boutiques and gourmet food shops in the capital's chic seventh arrondissement.
In the daily Le Monde on Saturday, the heads of the Catholic, Muslim, Protestant and Jewish communities urged President Francois Hollande's government to allow more time for a public debate on what they said was a foundation of society.
In the same edition, a front-page editorial called the plan "a legitimate, necessary and progressive reform" and said it will have been amply debated in public by the time the bill has its first reading in parliament in January.
Also on Saturday, Pope Benedict encouraged French bishops visiting him in the Vatican to oppose the reform, saying "the Church's voice must make itself heard relentlessly and with determination".
Hollande made gay marriage one of his campaign promises and his government plans to legalize it by mid-2013. It will include adoption rights for gay couples, but not the option of assisted procreation methods such as artificial insemination.
Alexandre and Emilie Philippe, a young Parisian couple marching on Sunday with two of their four small children, said they knew the law would eventually pass. "But we wanted to show our disapproval," he said.
Carrying a sign saying "One papa + one mama - what else?", she said: "We're doing this for our children. Their generation is the one that will be affected by this."
Initially caught off guard, the government has been hitting back at opponents of same-sex marriage. Social Affairs Minister Marisol Touraine said Saturday's turnout was "insignificant" and no better than the crowds that opposed civil unions in 1999.
The civil unions created back then were quickly accepted and their annual total is now approaching that of traditional marriages. Only 6 percent are undertaken by same-sex couples.
Organisers and police disagreed on the turnout. On Sunday, organisers estimated the Paris crowd at 18,000 and police at half that number.
On Saturday, organisers said 200,000 people demonstrated in the French capital, compared with a police estimate of 70,000. Thousands more marched in Lyon, Marseille and other major towns.
Lyon Cardinal Philippe Barbarin joined the march there along with Kamel Kabtane, rector of the Grand Mosque of Lyon, and other Muslim leaders. Toulouse Archbishop Robert Le Gall marched with the protesters there on Saturday.
At Sunday's protest, Rev Regis de Cacqueray, head of the French district of the ultra-traditionalist Society of Saint Pius X (SSPX), marched with priests in long black cassocks and laymen waving flags of far-right Catholic and royalist groups.
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.
(Additional reporting by James Regan and Chine Labbé; Writing by Tom Heneghan; Editing by Alison Williams)