Parts of central Paris have been brought to a standstill as hundreds of thousands of people demonstrated against gay marriage and adoption.

Three columns of protesters, waving pink and blue flags showing a father, mother and two children, converged on the Eiffel Tower from different meeting points in Paris.

Many came after long train and bus rides from the provinces.

Organisers insist they are not against gays and lesbians but for the rights of children to have a father and mother.

Slogans on the posters and banners approved by the organisers included "marriagophile, not homophobe," "all born of a father and mother" and "paternity, maternity, equality".

Organisers claimed 1 million people had protested, while police put the number at 340,000 - high even in protest-prone France.

Patrice de Beer, a political analyst and former editor of Le Monde, observed one part of the demonstrations at close hand.

"They've been around here for three or four hours. It was very, very noisy," she said.

"This demonstration - organised by the conservative parties and the churches - is strongly against this bill.

"The main slogan I could hear from here is 'Hollande, the French president, you can stick this reform in your bottom'."

At the protest, a comedian with the stage name of Frigide Barjot called on the president to abandon his plans, noting the diversity of the crowd in opposition.

She said those against gay marriage are multicultural, multi-religious, multi-philosophical and multi-sexual.

Contentious issue

The legislative change, due this year, has become an unexpectedly contentious issue for president Francois Hollande in a country that introduced civil unions about a decade ago.

His opponents' campaign has dented public support and forced deputies to put off a plan to allow lesbian couples access to artificial insemination.

An opinion poll of almost 1,000 people, published at the weekend, suggested 56 per cent of France supports gay marriage, down on previous polls, and 50 per cent disapprove of gay adoption.

Nevertheless, de Beer does not believe the protests will be enough to make the president to back down.

"They represent a very active but small minority within the French population, which in its majority is in favour of what is called here wedding for all - which is in fact wedding for gay couples," she said.

"I don't think that President Hollande is going to change his line anyway.

"He has been in favour of this reform.

"It was one of his popular promises during his election campaign and for him it would be impossible to backtrack on this reform which is accepted by a majority of the French people.

"He would lose face right in the middle of economic and social reforms that he is trying to implement.

"He just can't afford backtracking."

ABC/Reuters