The wife of Italian Prime Minister Silvio Berlusconi, who is entangled in a spate of scandals involving other women, says she wants a divorce because she can no longer stop him from "looking ridiculous before the world".

In a revised edition of a biography, Veronica Lario said she had no choice but to leave Mr Berlusconi after newspapers said he had attended an aspiring model's 18th birthday party.

He told her he was at a conference.

"It was the umpteenth lie. Better to finally respect myself, better to divorce," Ms Lario said in the book titled Tendenza Veronica (Veronica's Trend).

"I cannot condemn myself to be his wet nurse and I cannot stop him from making himself ridiculous before the world."

Ms Lario publicly demanded a divorce in early May from her husband of 19 years, accusing him of "frequenting minors".

Mr Berlusconi has denied any indecent relationship with Letizia Noemi, whose 18th birthday party he attended in April and to whom he gave a €6,000 necklace as a gift.

He has denied that anything "spicy" happened between them. "I think that I have no choice but to separate... He would tell me another lie and this time I could not stand it," Ms Lario says in the book by journalist Maria Latella.

Ms Lario, Berlusconi's second wife, met him in 1980 and bore him three children before they married a decade later.

She said that for many years she had silently endured Mr Berlusconi's behaviour with other women.

"I've reached the end of the road. Ten years ago I was not ready but now I can say: I am leaving this man."

She spoke to Ms Latella in the spring, before another scandal broke over allegations that Mr Berlusconi spent the night with call-girl Patrizia D'Addario in his Rome residence in November.

Mr Berlusconi, notorious in diplomatic circles for a string of gaffes, asked his wife's forgiveness after Ms Lario said in a public letter to a newspaper that he had wounded her dignity.