Kolkata Police chief Rajeev Kumar is a "potential accused" in the investigation into chit fund scams.

Taking a stand contradictory to Congress party's high command over the CBI controversy, West Bengal state party president Somen Mitra today asked why Kolkata Police commissioner Rajeev Kumar is avoiding interrogation by the central investigating agency in the chit fund scam.

"If he (Kumar) is not in the wrong then why is he avoiding the CBI?" Mr Mitra asked.

The state unit's position is a contrast to that of Congress president Rahul Gandhi, who on Sunday called up Chief Minister Mamata Banerjee and extended support to her.

Ms Banerjee is on indefinite dharna in the city since Sunday night, protesting against the CBI action, at the spot where she had sat on a 26-day fast against acquisition of farm land for the Tata Motors project at Singur in 2006.

"The entire opposition will stand together and defeat these fascist forces," the Congress president had tweeted.

Mr Mitra, who was a member of the TMC from October 2009 to January 2014, said "our (state Congress) fight against the BJP and the Trinamool Congress will continue" and questioned the timing of the CBI action.

An all-out war broke out between the Centre and the Mamata Banerjee government on Sunday with the West Bengal chief minister starting what she called "Save India" sit-in to protest against CBI's attempt to question Kolkata Police chief Rajeev Kumar in chit fund scam.