The BJP government on a damage-control bid asked why Bengal chief minister Mamata Banerjee was trying to protect Calcutta police commissioner Rajeev Kumar by sitting on dharna because the CBI wanted to question him regarding the Saradha scam.

Union law and justice minister Ravi Shankar Prasad asked 'kya hai police commissioner mein (what's so special about the police commissioner)' at a news conference. Minutes before, he said the 'razdaar (the keeper of secrets)' knows something.

Prasad also reminded the assembled journalists that Congress and Left leaders had filed the case in Supreme Court seeking a probe into the Saradha deposit-default scam.

The matter has snowballed when the CBI's credibility as the main domestic probe agency is low because of the messy changes at the top recently.

Prasad is not the only BJP leader and minister who spoke out on the Saradha scam.

Union home minister Rajnath Singh earlier in the day warned of a constitutional breakdown in Bengal in the wake of the Calcutta police-CBI face-off. In the Lok Sabha, Singh said the move to stop the central investigating agency from performing its duty was 'unprecedented'.

An all-out war broke out between the Centre and the Mamata Banerjee government on Sunday over the CBI's attempt to question the Calcutta police commissioner.

Rajnath described the action against the CBI team - the central probe agency's officers were allegedly detained at a police station in Calcutta - as a threat to the federal political system of the country.

'There may be constitutional breakdown in West Bengal.... Under the Constitution, the central government has been vested with the power to maintain normalcy in any part of the country,' he said.

Earlier, Opposition parties in the Lok Sabha attacked the government over the alleged misuse of central agencies against political rivals, saying it flouted democratic norms.

Members of the Trinamul Congress, the Biju Janata Dal, NCP and the Samajwadi Party spoke against the CBI move to question the Calcutta police chief.

The Supreme Court on Monday agreed to give an urgent hearing to the CBI's plea alleging destruction of electronic evidence related to the Saradha scam case by the Calcutta police commissioner and said it will come down heavily on him if he 'even remotely' tries to destroy evidence.

The apex court said it will hear on Tuesday the probe agency's applications which alleged that an extraordinary situation has arisen in which the top police officers of Bengal police are sitting on a dharna along with a political party in Calcutta.