Tax fraud tip-offs increased fourfold in crisis-hit Greece last year, the Kathimerini daily reported on Sunday.According to the newspaper, Greece\'s financial crimes squad received 18,500 reports in 2010, up from 4,500 the previous year. The squad\'s chairman told Kathimerini that most of the cheats reported to his unit owned \"shops that do not provide receipts, or were doctors and lawyers.\"Under intense pressure from its creditors, debt-laden Greece has committed to a draconian austerity plan, which includes a long-overdue crackdown on tax fraud.Despite the surge in whistleblowers, experts have warned that a tax hike decided in June could lead to mass evasion.