"Sonia Gandhi is the 'bahu' (daughter-in-law) of the country. BJP is trying to trap her in the chopper deal," Prasad told reporters after emerging from a meeting with JNUSU President Kanhaiya Kumar.
"It's an attempt by the BJP to harass a 'bhali aurat' (nice woman) ... This is too much," he said.
The RJD chief, whose party is a partner in the Grand Secular Alliance in Bihar with JD(U) and Congress, questioned the "insincerity" of NDA government in getting the helicopter deal probed in the two years of its rule.
Earlier in the day, Bihar Chief Minister and JD(U) President Nitish Kumar had also attacked BJP-led NDA government over AgustaWestland helicopter deal and hit out at Sonia Gandhi over it.