The BJP, which is strongly entrenched in power at the centre, has been relentlessly going after ruling regional parties in states like West Bengal, Delhi, and Telangana.
The ED had arrested Chatterjee, who is also the Trinamool Congress secretary-general, on July 23 in connection with its investigation into alleged irregularities in the recruitment drives by the School Service Commission.
TMC asserted the party will not interfere politically if any leader was found to have done anything wrong.
Opposition BJP went hammer and tongs over the development and demanded a reply from Chief Minister Mamata Banerjee.
Tharoor's statement comes a day after his Twitter post on Trinamool Congress MP Mahua Moitra's Goddess Kali remark on Goddess Kaali was termed as 'personal opinion' by his party.
Moitra on Tuesday triggered a controversy with her remarks that she has every right as "an individual to imagine Goddess Kali as a meat-eating and alcohol-accepting goddess".
The Mamata Banerjee-led party said people's mandate was insulted in Maharashtra as the BJP resorted to horse-trading to bring down a democratically elected government.
It also breaks the myth that the minority community in India and West Bengal votes blindly in favour of whoever their religious leaders ask them to.
While BJP managed to win only 12.8 per cent of the votes polled in Ballygunge, Asanol saw the party's vote share dropping to 30 per cent from 51.16.
The incident took place within an hour after the alleged murder of a Trinamool Congress panchayat leader on Monday, DGP Manoj Malaviya told reporters in Kolkata.