"It is his personal opinion. I suggest that since he is a part of the government, he should have given the suggestion to the government rather than making any such statement in public. Party forum is also open for giving suggestions," Congress spokesman Rashid Alvi said.
The disapproval came on a day when the victim's family said it had no objection to naming the proposed law after their daughter as suggested by Tharoor on Twitter a day before.
The minister of state for HRD had also favoured making public her identity, wondering what interest was served by keeping her name under wraps.
But home ministry officials said the Indian Penal Code (IPC) and the Criminal Procedure Code (CrPC) do not have a provision for naming any legislation after an individual.
"No law has been named after any person in India. One has to see the case in national perspective. The issue has wide repercussion while registering offences. This girl has been a catalyst to changes in the anti-rape law but naming is not an option," an official said.
"It would have been better had he given this advice to the government and the home minister has to take the decision," Alvi said.