Jethmalani had criticised the party's opposition to the appointment and also demanded Gadkari's resignation for alleged business irregularities.
Senior BJP leaders Sushma Swaraj and Arun Jaitley had opposed Sinha's appointment, saying the government should have waited as the report of the select committee on the lokpal bill had recommended that CBI directors be chosen through a collegium and not at the Centre's discretion.
Jethmalani implied the attack was instigated by a rival aspirant to the post and had welcomed the PM's move.
"We were concerned only and only with institutional reforms. Our suggestion wasn't person-centric," Jaitley said.
Jethmalani received support from party MP Shatrughan Sinha, who said, "The appointment was done in a fair and transparent manner."