As Silvio Berlusconi yesterday tried to shore up his position by declaring himself irreplaceable as Italy's head of government, a court in Milan was told it had been "amply demonstrated" that he was guilty of bribery.

"I am, and not only in my own opinion, the best prime minister who could be found today," he told a press conference. "I believe there is no one in history to whom I should feel inferior. Quite the opposite."

The problem, he explained, was that "In absolute terms, I am the most legally persecuted man of all times, in the whole history of mankind, worldwide, because I have been subjected to more than 2,500 court hearings and I have the good luck – having worked well in the past and having accumulated an important wealth – to have been able to spend more than €200m in consultants and judges ... I mean in consultants and lawyers."

His comments came as Laura Bertole, Milan's chief prosecutor, was speaking at the opening session of an appeal launched by Berlusconi's former legal adviser, David Mills, against his conviction for accepting a bribe from the TV magnate in the 1990s, when Berlusconi was in opposition.

Bertole, speaking two days after Berlusconi was stripped of his legal immunity, said Mills, the estranged husband of the Olympics minister, Tessa Jowell, had "first confessed, then retracted, indicating witnesses who have contradicted his words [and] his version of events".

Mills, who was found guilty in February of accepting a $600,000 bribe (£375,000) for distorting his evidence in Berlusconi's favour, acknowledged in a statement to prosecutors that he later retracted that the money came from his former client. The British lawyer subsequently identified a Neapolitan ship owner, Diego Attanasio, as the true source of the funds. Attanasio denies Mills's claim.

Bertole asked the judges not to agree to two requests by Mills's lawyer: to call Berlusconi as a witness and to gather evidence from Gibraltar. Berlusconi's counsel has said the prime minister would be available to testify if the court gave the go-ahead. Under Italian law, defendants are allowed up to two appeals that must be held before charges are extinguished by a statute of limitations that, in this case, would come into effect next April. The speed with which the first appeal court intends to dispatch its business is bad news, not just for Mills, but also for Berlusconi, his co-defendant until the immunity law took effect last year.

The case against the prime minister will have to be restarted and will almost certainly be "timed out" before a conclusion is reached. But a definitive conviction of his former co-defendant would, by implication, mean Berlusconi was equally guilty of having bribed him.

On Wednesday, the constitutional court threw out a law introduced by Berlusconi's government giving him immunity from prosecution. After venting his spleen on those he held responsible for the decision, the prime minister yesterday turned his attention to suggestions that he might step down for the good of the country. Italy's main opposition group, the Democratic party, has not called for Berlusconi's resignation, but a smaller opposition party said he should go.

Irate at the constitutional court decision, Berlusconi has lashed out at perceived antagonists including the president, Giorgio Napolitano, whom he blamed for not using his influence to sway the judges in his favour.

He also upset women, furious that he used the looks of a female opposition politician, Rosy Bindi, to insult her during a live TV discussion of the court's decision. A Facebook site offering support to Bindi had attracted more than 7,000 adherents by last night.

One of Berlusconi's cabinet, the youth minister, Giorgia Meloni, disassociated herself from his comment that Bindi was "more beautiful than intelligent". Meloni said: "I regret Berlusconi's remark."