Thousands of opponents of gay marriage marched through Paris yesterday in a last-ditch protest before a law allowing same-sex union and adoption is passed tomorrow.

About 50,000, most of them older people and families with children, waving pink and blue flags massed behind a banner reading: ‘All born of a mum and a dad.’

Although it ended peacefully, riot police had been on standby after a series of violent demonstrations outside the French parliament earlier this month.

Yesterday’s march had been hastily organised after the law’s passage was sped up to avoid a big rally set for next week.

‘We warned the president back in November that we would not give up and that we would do everything to stop this law being passed, or to get it repealed if it is adopted,’ said protest organiser Alberic Dumon.

Numerous opinion polls have shown that a majority of French people support gay marriage but far fewer agree that homosexuals should be allowed to adopt children.

Senior religious leaders have condemned the same-sex marriage and adoption laws and many were expected to join yesterday’s protest.

The extremist arm of the movement has seen public stalking of government ministers and a spate of homophobic attacks around the country.

And in January, around 350,000 protesters massed under the Eiffel Tower and tore up the lawns beneath it.

Paris mayor Bertrand Delanoe, one of few French public officials who is openly gay, headed a rival march yesterday in favour of same-sex marriage and said that it was too late for anything to derail the law.

Hollande, who is grappling with the lowest popularity ratings of any recent French president as unemployment surges above 10 per cent, hoped to win some glory from passing a reform already in place in a dozen other countries.