MILAN — The prosecution of former Prime Minister Silvio Berlusconi on charges of paying for sex with an under-age prostitute and then abusing his powers to cover it up concluded on Monday with a call for a six-year jail sentence and a lifetime ban from public office.

In detailed closing arguments that lasted nearly all day, Ilda Boccassini, a prosecutor in the case, said that Mr. Berlusconi was aware that the woman, Karima el-Mahroug, was a minor when he met and subsequently had sex with her.

Ms. Boccassini said Ms. Mahroug, known as Ruby Heart-Stealer, was “part of a system of prostitution organized to satisfy the pleasure of Silvio Berlusconi” at parties held at his villa outside of Milan while he was in office. Documents presented to the court showed that in the three years since the alleged sexual encounter took place, Mr. Berlusconi, 76, a billionaire media executive, gave Ms. Mahroug more than $5.8 million.

Both Mr. Berlusconi and Ms. Mahroug deny that they had sex. He has insisted that nothing untoward ever happened at the parties at his residences.