On his Facebook post, Sandhu, a former journalist wrote, "I wish I had known about Harmail Singh Tohra's involvement in the unfortunate attack on AAP MP Dr Dharamvir Gandhi in 2014 Lok Sabha polls. I would have opposed his entry".
"Now this person must publicly apologise for his role in the attack," he said.
"Besides, he should prove that he is committed to AAP's strategy before being made a candidate for any polls," he further said.
Interestingly, Sandhu was also present on the occasion.
More From This Section
When contacted, he confirmed about his comments on his Facebook post.
Sandhu, who is a chairman of party's Punjab Dialogue, urged the party to be "more careful" while inducting people in future.
"Obviously, we need to be more careful in inducting people left and right and broad-base the screening process for the same," he said in his post.
He was suspended by AAP in 2015 for allegedly involved in "anti-party activities".