A close adviser to the Greek prime minister resigned on Tuesday after being convicted of trying to pervert a criminal investigation, the latest scandal to beset the troubled conservative government. A court in Crete sentenced Yannis Kefaloyannis, a former minister and elder statesman of Greece's ruling New Democracy party, to a 12-month suspended sentence for trying to protect criminals during an enquiry into cannabis mafias on the rugged Mediterranean island. He has appealed against the ruling. “Yannis Kefaloyannis will not carry out his duties any more as an unofficial adviser to the prime minister ... until the procedure is completed in the appeal court,” a brief statement from the prime minister's office said. The scandal comes at a bad time for Prime Minister Costas Karamanlis's government, which lost its lead in opinion polls to the opposition Socialists last week for the first time since winning power in 2004, amid public anger at corruption, tax rises and unpopular economic reforms. The departure of 76-year-old Kefaloyannis, a scion of one of Crete's most powerful political families, comes less than two weeks after Merchant Marine Minister George Voulgarakis resigned over allegations of improper property deals. Karamanlis, who initially supported Voulgarakis, is under mounting pressure from within his party to stamp out scandals threatening its slender majority of 152 in the 300-seat parliament. Some political analysts believe he may be forced to call elections next year as his administration faces several investigations.