A French court refused on Thursday to recognise as a woman a transsexual man who changed gender but remained married to his wife, arguing that to do so would be to recognising gay marriage.

Chloe Avrillon, 41, is still called Wilfrid on state identity documents and went to court to seek judicial recognition as a woman, as several non-married French transsexuals had done successfully before her.

The case proved a challenge for the court, however, as Avrillon is still married to her wife, Marie, mother of their three school age sons.

Marie is happy to remain in a lesbian relationship with Chloe, but the court ruled it could not recognise the change in gender as that would de facto create a homosexual marriage, which is still banned in France.

"Marriage is the union between a man and a woman. The court cannot, in judicially modifying the sex of a married person, create a legal situation forbidden by law," the court in the Breton port of Brest said.

"To modify the sex mentioned on a birth certificate of a married person would result not in taking note of but in creating a situation of marriage between persons of the same sex," said the ruling, seen by AFP.

Avrillon's lawyer, Emmanuel Ludot, said his client intended to appeal and said he would lodge a request for a constitutional ruling on the issue.

"Of course, a change of identity would be allowed him if he had just got divorced," he said after the ruling.

"What kind of blackmail is this, where we're putting pressure on a man that has become a woman, telling him:'If you don't divorce you'll just have to stay a woman'?" he complained.

Had Avrillon not already been married to Marie for 15 years he could have formed a homosexual couple under France's civil partnership law, and enjoyed some of the same legal and tax protections of a married couple.

But homosexual marriage is not yet recognised in France, despite years of campaigning by gay rights activists.

"Recognising my identity as a woman will allow me to be myself," Avrillon, a government worker, told the daily Le Parisien in October.

"It will also be much more practical in everyday life -- sometimes they refuse my identity card when I write a cheque or go to pick up a parcel. And in terms of tax allowances, married status is much better," she said.

"Marie has always been a homosexual. It just happens that she fell in love with a refined and effeminate boy. That boy was me," she said.

The couple had dared hope the gender change would be recognised after a hearing in October, at which government lawyers told the court they had no objection to the switch nor to the pair remaining married.

"Justice was really just," Avrillon had said after the earlier hearing, which Ludot had described as a real breakthrough for civil rights.

"I wept tears of joy. It's such a wonderful present, a real step forward for society, for moral values, tolerance and human rights," she had said, fully expecting the court to update her status, according to reports.

France's opposition Socialist Party has promised to permit homosexual marriage and adoption if it wins next June's legislative elections, but President Nicolas Sarkozy's right-wing majority is divided on the issue.

Six lawmakers from Sarkozy's UMP have urged the party to add gay marriage to its manifesto, but a conservative faction remains firmly opposed, and party leader Jean-Francois Cope has said there will need to be a debate.

Ten of France's fellow EU member states have permitted gays to marry, but France's first homosexual marriage in 2004 was later annulled in the courts.