(ANSA) - Rome, July 26 - A top prosecutor investigating alleged negotiations between the Italian State and the mafia was authorized to leave his post for a UN position in Guatemala on Thursday. The Italian judiciary's self-governing body CSM voted to allow Antonio Ingroia, a deputy chief prosecutor in Palermo, to accept a 12-month appointment to the UN Commission Against Impunity in Guatemala, heading up the anti-narcotics investigation unit. The vote was split amid controversy surrounding Ingroia's ongoing investigation into suspicions that high-ranking politicians entered negotiations with Cosa Nostra in a bid to stop a series of bomb attacks that claimed the lives of anti-mafia judges Giovanni Falcone and Paolo Borsellino in 1992. The probe recently drew the intervention of President Giorgio Napolitano over concerns that Palermo prosecutors had surpassed their powers by wiretapping conversations between the head of state's legal advisor and former Senate speaker Nicola Mancino. The prosecutors had allegedly failed to comply with the legal obligation to immediately destroy the recordings. Napolitano has appealed to the Constitutional Court on the grounds that the constitution forbids investigating the head of state unless he is suspected of high treason or attacking the constitution itself. Ingroia's office has also been at the center of an investigation into allegations that former premier Silvio Berlusconi was a victim of extortion by his former aide Marcello Dell'Utri, a senator in the ex-premier's People of Freedom party. Dell'Utri is set to have a retrial after receiving a seven-year jail sentence for allegedly helping the mafia. But in its explanation of its decision to order a retrial, the Palermo court said there was evidence that Dell'Utri had acted as an intermediary with the mafia for Berlusconi, handing out "substantial sums" of money for protection.