The development followed the arrest of chartered acountant Rajesh Kumar Agrawal by the Enforcement Directorate on May 22. Agrawal is alleged to have aided in llegal transactions involving Lalu's kin.
Officials said the department has asked Bharti, a Rajya Sabha member, and her husband Shailesh Kumar to appear before the investigating officer (IO) here in the first week of June.
The department had on May 16 searched multiple premises of about two dozen entities connected to this case and seized documents and computer hardware.
The couple are alleged to have links with a firm-- Ms Mishail Packers and Printers Private Limited-- which is suspected to have entered into benami deals for purchase of a farm house in Delhi's Bijwasan area.
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Certain other property deals are also under the scanner of the taxman, they said.
I-T department officials had said they will apply provisions of the newly enacted Benami Transactions Act, 1988, which became operational from November 1 last year, in this case. The law provides for a maximum punishment of seven years in jail and a fine.
Tax department officials had said Lalu's kin held some of the properties under their scanner in a 'benami' way. Benami properties are those in which the real beneficiary is not the one in whose name the property has been purchased.
The RJD chief, however, sought to put up a brave face after the raids, saying he was "not scared at all" and will continue to fight against "fascist forces".
"BJP mein himmat nahi hai ki Lalu ki awaz ko daba sake... Lalu ki awaz dabayenge to desh bhar me karoron Lalu khare ho jayenge... Main gidarbhabhki se nahi darne wala hoon (BJP does not have the courage to stifle my voice... If it tries to silence one Lalu, crores of Lalu will come forward. I am not scared of empty threats)," he had said in a series of tweets after the search operation.
Union minister Ravi Shankar Prasad had alleged that these transactions were a case of "quid pro quo", suggesting that money was paid in return for favour, as they dated back to the period when Lalu was the railway minister, and dared Bihar Chief Minister Nitish Kumar to take action against him.
Lalu's RJD is a constituent of Bihar's ruling coalition led by Kumar.