Frederic Mitterrand has rejected criticism from the far right
France's Culture Minister Frederic Mitterrand is facing intense pressure over a book he wrote that described paying for "young boys" in Thailand.
The book was written four years ago, before he joined the government, but is back in the headlines following his impassioned support for Roman Polanski.
Polanski has been arrested in Switzerland on child sex charges.
Mr Mitterrand, nephew of late President Francois Mitterrand, is expected to defend himself on TV later on Thursday.
Mr Mitterrand has come under attack from right and left.
In his 2005 book The Bad Life, he wrote: "I got into the habit of paying for boys," saying his attraction to young male prostitutes was not dimmed despite knowing "the sordid details of this traffic".
Born in Paris, 21 August 1947
Nephew of former Socialist President Francois Mitterrand
Former TV presenter, documentary maker and writer
Appointed head of the French Academy in Rome in 2008
Named by Nicolas Sarkozy as culture minister in June 2009
"All these rituals of the market for youths, the slave market excited me enormously... the abundance of very attractive and immediately available young boys put me in a state of desire."
Mr Mitterrand, 62, has denied being a paedophile, saying the term "boys" was used loosely.
The account of cruising for prostitutes in Thailand attracted little attention when it was published in 2005, when Mr Mitterrand was a TV personality.
He did not share his uncle's socialist politics, and was brought into the centre-right government by President Nicolas Sarkozy in June 2009.
But his strong defence of Polanski has brought the book back into the public eye. Polanski faces deportation to the United States for having had sex with a 13-year-old girl in 1977.
Mr Mitterrand said the US' behaviour, in seeking his extradition, was callous and "horrifying".
Socialist Party spokesman Benoit Hamon told Reuters: "As a minister of culture he has drawn attention to himself by defending a film maker accused of raping a child and he has written a book where he said he took advantage of sexual tourism. To say the least, I find it shocking."
Marine Le Pen, vice president of the right-wing National Front, read excerpts of Mr Mitterrand's book aloud during a television interview, and said it left "an indelible stain on the government".
She called for the culture minister to step down.
"Resign, Mr Mitterrand and perhaps, afterwards we'll be able to give lessons to other people," she said.
Mr Mitterrand said it was an honour to be dragged though the mud by the National Front, and criticised the Socialists for making common cause with the extreme right.
A senior aide to President Sarkozy, Henri Guaino, on Thursday backed the minister, saying the row was "excessive and quite undignified".
But the BBC's Emma Jane Kirby, in Paris, says that the revelation that a senior cabinet minister was involved in sex tourism, just as the country holds negotiations with Thailand to discuss ways of fighting it, will inevitably embarrass Mr Sarkozy's government.