Abu Hasem Khan Chowdhury, who represents West Bengal's Malda South Lok Sabha constituency, reached the CBI office at the CGO complex here.
Reacting to Abu Hasem Khan Chowdhury's summoning, state Congress president Adhir Ranjan Chowdhury said it was not a matter for concern for the party.
"Calling for questioning doesn't mean he has been made an accused. We have been supporting the CBI probe and extend all cooperation to it. It's not a matter of concern," said Adhir Ranjan Chowdhury.
Abu Hasem Khan Chowdhury, who had drawn the attention of then prime minister Manmohan Singh to the mushrooming Ponzi schemes in West Bengal and urged action against them, later retracted and batted for the tainted Saradha Group.
Contradicting his September 2011 letter to Manmohan Singh, Abu Hasem Khan Chowdhury in March 2012 wrote to the prime minister again, saying: "The company (Saradha) is conducting a prosperous and successful realty business in West Bengal with some investment in the media and health sectors." He said he was withdrawing his earlier complaint against the group.
But after the scam came to light, Abu Hasem Khan Chowdhury admitted batting for the Saradha Group was a "mistake".
Having arrested four people, including Trinamool Congress leader and former IPS officer Rajat Majumdar, the CBI recently grilled CPI-M leader Rabin Deb in connection with the scam.