"Every child in the country is asking the same question," Mishra told IANS. "I stand by my (Tuesday) remark. I have doubts about Modi's agenda for sure."
Mishra had tweeted on Tuesday: "Do we have an ISI agent as PM now?? Its very serious the way PM is surrendering to anti-India forces?"
Mishra's comments followed the Modi government decision to allow a Pakistani team to probe the terror attack on the IAF base in Pathankot in Punjab.
Delhi Chief Minister and Aam Aadmi Party leader Arvind Kejriwal on Tuesday asked Modi to "apologize to the nation" for allowing the Pakistani team to probe the terror attack.
BJP spokesperson Sambit Patra and other BJP leaders attacked Mishra over his remarks.
Delhi Bharatiya Janata Party leader Praveen Shankar Kapoor on Wednesday accused Mishra of indulging in "cheap politics". He told IANS: "They have no understanding of international politics."