The agency, sources said, arrested 40-year-old Prashanto Naskar after few hours of interrogation at its Salt Lake office here.
"Naskar has been working as an agent of Saradha schemes in the Bishnupur area of the state for long. He was also active as a political muscleman in the area and had close connections with a TMC leader and strong links with Sen," a source said.
The ED, the sources said, found Naskar was allegedly in possession of a huge number of movable and immovable assets in Bishnupur area and used to extort money from depositors in lieu of getting them huge returns.
Prominent among those arrested by the agency in this case include Sudipta's wife Piyali and son Subhojit who were apprehended last year.
Also Read
Naskar will be produced in a court here tomorrow for extension of his custody after which he is expected to be confronted with a number of seized documents and statements made by other accused in the case.
Sources said Naskar holds, in a 'benami' way, vast tracts of land in and around Bishnupur and lives in a house which is plush with modern facilities and a large swimming pool which is suspected to have been procured through illegal means and from the "proceeds of crime" of the scam.
ED which has questioned various TMC MPs and other people in this scam case, including Sen, has attached assets worth Rs 500 crore till now in this probe.