A minister and two legislators of the of Trinamool Congress have been arrested in the case.
The Trinamool Congress is to move the Supreme Court against what it calls the "blatant misuse of CBI by the Centre to settle political scores". Former Union minister Kapil Sibal will represent the party in the court, according to top Trinamool sources.
The ruling party in West Bengal has been under pressure, with one of its ministers and two legislators being arrested in the case. They include transport and sports minister Madan Mitra, Rajya Sabha MP Srinjoy Bose, and Kunal Ghosh, who is also a Rajya Sabha member but suspended from Trinamool.
Chief Minister Mamata Banerjee - who declared yesterday that she would personally focus on day-to-day affairs of the party - has been accused of personal involvement in the scam by Mr Ghosh, the first party MP to be arrested.
Ms Banerjee has alleged that the BJP, which is trying to gain a foothold in the state, is using the Saradha scam to get back at the Trinamool Congress since it cannot target the party politically.
"The use of CBI against us in the Saradha scam is a classic case of how the institution is used for political vendetta," said Mr Derek O'Brien, who is also a Rajya Sabha member from Trinamool Congress . "We will fight this politically, legally and in every way possible in a parliamentary democracy," he added.
Asked if the Trinamool was going to court because the CBI probe is hurting the party, Mr O'Brien said, "Of course it is not hurting our party. But our belief is that if you through mud, the mud has to stick. Four months later, elections are coming up and the people will answer if the mud sticks or doesn't stick."
Sports minister Madan Mitra and party general secretary Mukul Roy have "done no wrong," Ms Banerjee reportedly said yesterday. "As they are deeply involved in the party organisation, a dirty political conspiracy is being hatched to put them behind the bars in order to weaken the party," a leader quoted Ms Banerjee as saying at a closed-door party meeting.