Silvio Berlusconi has ridiculed claims by Italian prosecutors that he paid 33 women for sex in a matter of months, saying he would need the stamina of a man one third his age to maintain such a private life.

The Italian prime minister, who will stand trial on April 6 on charges of having sex with an under age prostitute and abuse of office, launched an angry defence against the accusations, contained in court documents which were released on Tuesday.

"I'm 74 years old and even though I may be a bit of a rascal ... 33 girls in two months seems to me too much even for a 30 year old."

He condemned investigators for citing the women in their dossier because "for the rest of their lives they will be branded with an indelible label – prostitute".

He claimed to have a long-standing "girlfriend", whom he did not identify, who he said would never have allowed him to behave in such a way.

"If I'd done everything they say I've done, she'd have gouged my eyes out. And I can tell you, she has very long finger nails."

He said he had paid for dentistry bills, university tuition fees and medical treatment on behalf of his female friends, but that he did so out of personal generosity, seeking nothing in return. "I'm a walking charity," he said. "I'm happy to be able to do it."

He made the remarks to La Repubblica, a Left-leaning national newspaper that has repeatedly called for his resignation over the prostitution scandal.

Prosecutors have accused the 33 women of prostituting themselves for money, jewellery and other gifts with the billionaire tycoon, who denies all the allegations.

They include the Moroccan-born teenage erotic dancer at the heart of the scandal, Karima El Mahroug, now 18, better known by her stage name as Ruby the Heart Stealer.

Prosecutors say the women took part in "bunga bunga" orgies at Mr Berlusconi's imposing residence at Arcore, near Milan, involving "masks, stripteases and erotic dances" in which they "touched each other mutually or were touched in their intimate areas by Silvio Berlusconi."