Congress on 17 October said it was not obligated to answer any question on Robert Vadra as he did not belong to the party.
"First thing I want to ask is whether Robert Vadra, a member of the Congress, so that we answer on his behalf?" Congress leader Sandeep Dikshit said.
The senior leader also said that the BJP should establish facts if it has anything on alleged link between party President's son-in-law and fugitive arms dealer Sanjay Bhandari.
Vadra has found himself at the centre of a fresh maelstrom after a national news channel's expose alleging his link to Bhandari.
Dikshit said Vadra, and not Congress should come forward to explain the alleged link with the arms dealer.
On Tuesday, Union Minister Nirmala Sitharaman also questioned Congress' silence over the issue, saying party president and her son, Rahul's silence will be construed as acceptance of charges.
"Why Rahul Gandhi has remained silent. No tweets on the flats getting refurbished, no tweet on his brother-in-law getting money. Is the Congress leadership by remaining silence suggesting that yes they looked it but took it the other way? Can somebody from Congress cannot come and give this platitude but tell us how this happened," the minister had said.