Italy's former prime minister Silvio Berlusconi is under investigation again over accusations he corrupted witnesses in the so-called "bunga-bunga" trial, in which he was convicted to seven years in jail and given a lifetime public office ban.

Milan prosecutors alleged that Berlusconi and his lawyers, Niccolò Ghedini and Piero Longo, had paid "money and other benefits" to young women who had taken part in the infamous bunga-bunga parties, to give misleading evidence in the case.

Berlusconi, who has been banned from parliament over a separate tax fraud conviction, allegedly paid €2,500 (£2,000) every month to the 18 women who took part in the parties, held at the media mogul Milanese villa of Arcore.

Ghedini and Longo have denied accusations of witness tampering. Berlusconi repeated his own accusations, that judges and prosecutors had targeted him for political reasons.

"I will remain in place, more convinced than ever of the need to keep fighting for what I believe in profoundly," he said in a statement on Thursday.

Berusconi was being tried for allegedly paying 17-year-old Karima el-Mahroug, aka Ruby the Heart-stealer, for sex during the infamous bunga-bunga parties.

He was also accused of abusing power by calling a police station, where she was being detained on theft charges in May 2010, to put pressure on detectives to release her.

Berlusconi infamously told authorities that Ruby was a granddaughter of Egyptian president Hosni Mubarak and that her detention could cause a diplomatic incident. He was prime minister at the time.

The 77-year-old media billionaire has appealed against the sentence, which will not take effect until the whole appeals process is completed.