The Congress leader said it was due to CBI's "impartial" character that the party had "suffered immensely".
He said CBI sleuths picked up accused only after complete information regarding the wrongdoings of the person.
Singh's defence comes in the backdrop of UP Chief Minister Akhilesh Yadav's recent attack against Congress, alleging that anybody who does not act according to its wishes faces "persecution" through CBI.
Asked on Union Minister Beni Prasad Verma's attack on outside ally Samajwadi Party yesterday, Singh said, "any person is free to criticise the government's functioning but launching of personal attack cannot be justified".
The minister, in reply to media questions regarding increasing crime against women, said in 96% of such cases it was found that victims and attackers were known to each other.