Mr Sisodia will be questioned on Friday at 11 am.
The deputy chief minister was sent the notice today to join the probe, days after Chief Minister Arvind Kejriwal was questioned for over three hours in connection with the matter, police said.
Mr Prakash was allegedly attacked during a meeting at Mr Kejriwal's official residence on February 19. Police said the chief minister was present when the alleged assault took place.
The police have already questioned 11 AAP MLAs present at the chief minister's residence for the meeting.
Two of the party MLAs -- Amantullah Khan and Prakash Jarwal -- were arrested in the case.
Mr Kejriwal, his former advisor VK Jain and Mr Sisodia were also present in the meeting. Mr Jain was also questioned in the case.
On February 23, a police team had examined the CCTV system installed at the chief minister's residence in the Civil Lines area and seized the hard disk. The forensic report on the hard disk is still awaited.
The alleged assault on the chief secretary had triggered a bitter tussle between the Delhi government and its bureaucrats.
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