TV channels today showed Mann facing an angry group of people who were heard accusing the MP of being in inebriated state at the ceremony in Punjab.
Mann was not available for his reaction on the issue. He did even respond to SMS.
AAP denied any such incident, with senior leader Sanjay Singh terming it as a conspiracy against the party.
"This a conspiracy against the party and there is no iota of evidence against him. There is no question of any disciplinary action against Mann. Show us one evidence and we will act. Our campaign against drugs will continue," Sanjay Singh said.
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However, opponents attacked Mann.
"Mann's problem of alcoholism was well known to AAP PAC (Political Affairs Committee). He was not made the Leader of Parliament party, as he would often go to Parliament smelling of alcohol," claimed expelled AAP leader Prashant Bhushan in a tweet.
Another expelled AAP leader Yogendra Yadav wrote on his Facebook post: "I discovered it first in July 2014 when AAP had a meeting of all its Lok Sabha candidates. Mann was sitting next to me and was smelling of alcohol. I mentioned it to Arvind Kejriwal and he nodded. Around this time I heard rumours that Mann was going to the Lok Sabha sessions drunk. One of his fellow MPs confirmed it to me.
BJP leader Tarun Chug accused Mann of showing disrespect to Sri Guru Granth Sahib by attending the 'Bhog' ceremony and demanded "exemplary action" against him by AAP chief and Delhi Chief Minister Arvind Kejriwal.
Chugh said if this was the kind of leadership Kejriwal was trying to provide to Punjab, then people of the state would have to think twice before responding to AAP chief's calls and appeals.