Italy's highest court confirmed on Tuesday the acquittal of former prime minister Silvio Berlusconi, who had been charged with abuse of office and paying for sex with a minor. The ruling boosts his effort to retain his role as conservative leader.

At the first trial in 2013, Berlusconi, 78, was convicted and sentenced to seven years in prison. An appeals court in Milan overturned the ruling and acquitted him last year.

The Rome court, in a definitive ruling, rejected an appeal by Milan prosecutors to overturn the acquittal and hold a new trial.

Berlusconi was accused of paying for sex with former teenage nightclub dancer Kharima El Mahroug, known by her stage name "Ruby the Heartstealer", during "bunga bunga" erotic parties at his palatial home near Milan when he was prime minister in 2010.

He was also charged with abusing his authority to get El Mahroug, then 17, released from police custody over unrelated theft accusations.

Tuesday's ruling comes as the conservative leader is struggling to hold together his center-right Forza Italia Party and maintain a front-line role in Italian politics.

Berlusconi has just finished serving a community service order for corporate tax fraud and remains embroiled in several other legal cases. It is thought unlikely they will prevent him from trying to energize opposition to Prime Minister Matteo Renzi's plans to reform Italy's government.

Last month, Berlusconi pulled out of a pact with Renzi over reform of Italy's voting system and political apparatus, complaining that Renzi had excluded him from the choice of who should become the new head of state.

On Tuesday, Forza Italia voted against Renzi's political reforms in the Chamber of Deputies, but 18 party deputies wrote a public letter of dissent. They lamented a lack of internal party democracy and said they had only obeyed Berlusconi's instructions out of loyalty to their leader.

Forza Italia has steadily lost support since Berlusconi was convicted of tax fraud in 2013.

Reuters-AFP