PARIS - A French police union said Thursday it will ask the Paris public prosecutor to open an investigation of Culture Minister Frederic Mitterand on possible charges of soliciting a minor.

“We feel it is our duty to protect society against sexual predators, even if they are ministers,” the France Police trade union said in a statement.

The declaration came as a controversy escalated in France over an autobiography Mitterand wrote in 2005 in which he described travelling to Thailand to have paid sex with young men in brothels.

The affair began earlier in the week when the daughter of right-wing extremist Jean-Marie Le Pen read excerpts from the book on a television talk show devoted to the recent arrest in Switzerland of director Roman Polanski on a 32-year-old conviction for having sex with a 13-year-old girl.

Mitterand was one of Polanski’s earliest and most vocal supporters. However, Marine Le Pen said Mitterand himself was a paedophile, basing the accusation on several excerpts from his book La Mauvaise Vie (The Bad Life).

Among the passages she read was the following: “The profusion of very attractive and immediately available young boys puts me in a state of desire that I no longer have a need to brake or dim.”

The weekly Le Point published additional extracts from the book on its website Thursday, such as: “I can evaluate, imagine, tell myself stories regarding each boy; they are there for that, and I am too. I can finally choose. I have what I have never had, I have a choice.”

According to Le Point, President Nicolas Sarkozy read La Mauvaise Vie before naming Mitterand as his culture minister.

France Police said in its statement that “Mitterand’s confession in his book amply suffices to justify the opening of a preliminary investigation.”

Nothing in any of the excerpts cited suggests that the “young boys” with whom Mitterand apparently had sex were minors. However, the growing controversy, and the appearance that he was defending sex tourism, has mobilized the opposition and embarrassed the government.

Labour Minister Xavier Darcos told France Inter radio Thursday that Mitterand must respond to the accusations “other than with indignation”.

Socialist Benoit Hamon told Canal Plus television, “The question now is if Frederic Mitterand should resign or not.”

Mitterand has come under broad fire for his support of Polanski. On Wednesday he said he had reacted “too emotionally” at the time because he had spoken on the telephone with Polanski’s wife, the actress Emmanuelle Seigner.