The ruling against the Indian government's top anti-corruption official is a severe embarrassment for Singh [Reuters]

India’s chief anti-corruption official has resigned after the country’s highest court found his appointment by a committee headed by the prime minister to be illegal.

PJ Thomas stepped down as the Central Vigilance Commissioner (CVC) on Thursday after the supreme court in New Delhi overturned his appointment.

Thomas was appointed the CVC last September by a committee that included Manmohan Singh, the prime minister, and the home minister.

The third member - the leader of the opposition -  had objected to his selection since he faced allegations of irregularities while he was a senior bureaucrat in the early 1990s in the southern state of Kerala.

It was said that Thomas, as the food secretary in Kerala, had imported palm oil from Malaysia at a higher rate.

Thomas, however, protested his innocence and consistently claimed he was a victim of political conspiracy.

The supreme court , though, in its ruling said that the institutional and personal integrity of the CVC must be beyond doubt.

Elated by the ruling, Sushma Swaraj, the leader of the opposition, tweeted that the “dignity of the office of CVC has been restored”.

The court ruling, coming in the wake of a series of corruption scandals including a b$39bn telecom scam, is a serious setback for the federal government led by Singh.

Already under fire for supposedly being lax in tackling corruption, the government is likely to come under renewed attack from the opposition on the issue.

Several opposition parties, including the Bharatiya Janata Party, have called for a debate in the parliament on why the government had picked Thomas as the CVC.