In the latest blow to the Manmohan Singh government, Central Vigilance Commissioner P.J. Thomas quit Thursday after the Supreme Court struck down his appointment for his alleged involvement in a corruption scandal and raised the issue of "institutional integrity".

Six months after the Kerala bureaucrat was named the country's anti-corruption watchdog, the Supreme Court said the appointment by a high-powered panel, consisting of Prime Minister Manmohan Singh, Home Minister P. Chidambaram and opposition leader Sushma Swaraj, did not exist in law.