Under criticism for using the Central Bureau of Investigation to target opposition, the Bharatiya Janata Party asked on Monday if it was wrong to investigate corruption allegations.

Union Minister Ravi Shankar Prasad, who addressed a press conference as opposition criticism mounted on the BJP-led Centre for allegedly misusing the agency to target rivals,called the grand alliance that West Bengal Chief Minister Mamata Banerjee is apparently shepherding “an opportunist and corrupt alliance that has now crossed limits of decency”.

“What’s there in this police commissioner that Mamata Banerjee is sitting on a dharna to save him, when she kept quiet even when her top partymen were indicted and arrested in Ponzi scams,” Prasad, a senior BJP leader, said. “It seems he knows a lot and it’s important to save him. She seems to want to frustrate any attempts to conduct a fair investigation against this police officer.”

A row has erupted over CBI’s attempts to question Kolkata Police Commissioner Rajeev Kumar over allegations in a chit fund scam. Kolkata Police briefly detained CBI officials who visited the city to question the police officer.

“Mamata Banerjee’s on a dharna because she wants to project herself as the leader of this corrupt mahagathbandhan . Delhi Chief Minister Arvind Kejriwal has started this lowly idea of sitting on dharna, and now she’s taking it forward,” he said.

Prasad claimed that the CBI went to Kolkata after the police officer ignored three summons, and mocked the police officer’s participated in the dharna. He accused Banerjee of being intimidated by the support Prime Minister Narendra Modi and the BJP has found in the state.

Prasad also criticised the Congress party for its hypocrisy, saying that it was the Left and the Congress that had approached the Supreme Court to have the CBI investigate the Sarada chit fund allegations.