Addressing a press conference, Sitharaman said, "It's unfortunate that Arvind Kejriwal is mum on the serious assault on a woman member of his party who's also a Rajya Sabha MP. It is truly unbelievable and unacceptable.
"Kejriwal must tender an apology for the same."
Maliwal was allegedly assaulted by Bibhav Kumar at the Chief Minister's residence in Delhi's Civil Lines area on Monday.
Delhi Police had confirmed they received two calls from an unknown person within Arvind Kejriwal's residence but from a phone number registered to Maliwal alerting them to the harassment.
Maliwal later appeared at a police station in the area but left without filing a complaint.
Maliwal, a former NCW chairperson, recorded her statement with Delhi Police on Thursday. This was hours after the National Commission for Women issued a summons to Kumar.
Kejriwal mum on Maliwal case
Kejriwal gave no reaction when he was asked by a reporter at the joint press conference with other INDIA bloc leaders on Thursday.
SP chief Akhilesh Yadav, who was sitting right beside Kejriwal, remarked, "There are other more important issues than this to discuss."
Kumar had even accompanied Kejriwal to Lucknow, where the AAP supremo campaigned for the Lok Sabha elections.