July 22 (Bloomberg) -- Prime Minister Silvio Berlusconi's allies in the Italian Senate passed an immunity law that will protect the premier from prosecution until the end of his mandate in 2013.

The law will suspend two corruption trials against Berlusconi, 71, unless the premier asks his lawyers not to use it in court. The Rome-based Senate voted 171 to 128 to approve the measure, which the Chamber of Deputies passed on July 11.

The law will effectively end more than 14 years of legal troubles that Berlusconi has blamed on politically motivated prosecutors. With his popularity still high following the April election and an overwhelming parliamentary majority, Berlusconi has vowed to fight magistrates whom he accuses of trying to overturn the popular vote by prosecuting him.

``Berlusconi is too powerful to be put on trial,'' Alexander Stille, a professor of journalism at Columbia University in New York and author of a 2006 book on the premier, said in an interview. ``He has a huge majority and can basically pass anything he wants in Parliament.''

The opposition accuses the premier of changing the law for his own benefit. He is fueling a dispute with judges, whom Berlusconi has called ``a cancer on our democracy,'' to divert attention away from the struggling economy, lawmakers say.

Economic Crisis

``The prime minister is trying to make the justice system a symbol of the country's ills in order to resolve his personal problems and distract Italians from the current economic crisis,'' Lanfranco Tenaglia, an opposition spokesman on justice issues, said last week.

Italy's economy will expand 0.5 percent this year and the next, the slowest among the world's advanced economies, the International Monetary Fund said last week. Unemployment and the budget deficit are increasing and consumer prices are rising at the fastest pace in more than a decade.

Berlusconi won elections in April, taking office for a third time since 1994. During his campaign he promised tax cuts, a crackdown on illegal immigration and crime, and extraordinary measures to end a seven-month trash crisis in Naples.

In May, Berlusconi eliminated a property tax, lowered levies on overtime pay and began a push to clean up the trash that had piled up on the streets of Naples. On July 18, Berlusconi said the garbage emergency in the country's third-biggest city was over. A package of laws aimed at fighting illegal immigration and crime probably will be passed by parliament this week.

Justice Overhaul

Once the main campaign promises had been addressed, Berlusconi turned his attention to the justice system. He has now made the immunity law, an anti-eavesdropping measure, and a full- blown reform of the judicial system priorities.

The immunity measure ``is sober and balanced and respects the principles and values of the constitution,'' Justice Minister Angelino Alfano said today, opening the Senate debate. He promised to present his plan to overhaul the justice system, the least efficient in the European Union, in September.

Some polls indicate the policy shift is hurting his popularity. Confidence in Berlusconi fell for the first time in July since the April national vote, to 53 percent from 59 percent, according to a July 14 IPR Marketing of 1,000 voting-age Italians.

``It's the perception that he's acting in his own interest that's doing some damage,'' Maurizio Pessato, chief executive officer of SWG Srl polling company in Trieste, Italy, said. SWG polls have shown ``some fall'' in the premier's popularity in the last two weeks, Pessato said.

``But he had to get rid of this thorn soon or later, and he's right to do it now, quickly,'' he said. ``In a month's time, it will be forgotten.''

Popularity High

Even with the decline, Berlusconi's popularity rating remains more than twice as high as former Prime Minister Romano Prodi's was when he lost power in January.

Berlusconi has faced dozens of corruption trials since entering politics in 1994, when his first government fell after newspapers reported he was under investigation for bribing tax police. He was later acquitted of the charges. Since then, 789 prosecutors and judges have investigated him, forcing him to spend 174 million euros ($276 million) in legal fees, Berlusconi said on June 25.

The immunity law would put on hold two current trials. Berlusconi is charged in Milan with bribing U.K. lawyer David Mills to lie under oath. A verdict was due before the end of the year. In a separate case, the premier is accused of committing tax fraud when purchasing film rights for Mediaset SpA, his television company. Berlusconi and Mills deny any wrongdoing.

The new law will also shield the president of the republic and the speakers of both houses of Parliament from prosecution. Italy's constitutional court probably will be asked to review the measure. A similar immunity law passed by Berlusconi's allies in 2003 was struck down by the high court.

To contact the reporters on this story: Steve Scherer in Rome at scherer@bloomberg.net

Last Updated: July 22, 2008 14:18 EDT