Silvio Berlusconi was fighting for his political survival last night after he was stripped of his immunity from prosecution. The dramatic ruling will reopen several criminal trials against the Italian Prime Minister and could lead to the collapse of his government.

After two days of tense anticipation, the 15 judges of the Constitutional Court finally emerged to deliver a damning decision that will thrust the billionaire into a series of trials for fraud, corruption, tax evasion and bribery. The court’s ruling on constitutional issues is final and there can be no appeal.

The judgment follows months of lurid allegations against Mr Berlusconi, including detailed claims that he slept with a prostitute and promised showgirls who attended his parties positions in the European Parliament.

The highest profile case he faces involves the lawyer David Mills — the estranged husband of the Olympics Minister, Tessa Jowell — who was found guilty of accepting a $600,000 (£378,000) bribe from Mr Berlusconi to give false testimony in two earlier trials. Mills was convicted of perjury and sentenced to four and a half years in prison.

He has not begun his sentence and will start an appeal against it tomorrow. Mr Berlusconi had been a co-defendant but was exempted when the immunity law was passed soon after he assumed office last year.

An investigation into allegations of tax fraud concerning the sale of film rights by Mr Berlusconi's company Mediaset is also expected to be reopened, along with an inquiry into his alleged attempts to bribe senators to bring down Italy’s previous centre-left government.

The Opposition called on Mr Berlusconi to step down as Prime Minister but, speaking in front of his palace in Rome last night, he vowed to carry on. “The Constitutional Court is a political organ. The trials against me are a farce. Viva Italia and Viva Berlusconi!” he said with a clenched fist. He added that the court, the head of state and the media all favoured the Left.

“I will go on. We must govern for five years, with or without the law. I never believed because with a Constitutional Court with 11 left-wing judges, it was impossible that it would be approved.”

The 15 judges returned a majority decision, rejecting the legislation because it violated the Italian constitution on two grounds: first, it had not been subject to the greater scrutiny of constitutional procedures; second, it violated the principle that every Italian must be equal before the law.

Mr Berlusconi’s legal team had argued an Animal Farm defence, claiming that his unique duties as Prime Minister meant that he was “first above equals”. They argued that the law was necessary to prevent lawsuits distracting the most senior officials in the country from their electoral duty.

The 73-year-old has been dogged by legal challenges. He has been brought to court on charges of corruption, bribery, false accounting and illegal party financing but has always either been acquitted or won on appeal. In many cases time simply ran out under Italy’s statute of limitations.

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