"We have sent him a show-cause notice as the party has found that he has not been acting as per the constitution.
"He has sent notices to several party leaders in Punjab and has exceeded his brief," said a party leader who did not wish to be named.
When contacted, Singh refused to comment.
Party sources said the notice was sent yesterday by the National Disciplinary Committee, which comprises Ashish Khetan, Pankaj Gupta and Dinesh Waghela, all of whom are known to be close to party chief and Delhi Chief Minister Arvind Kejriwal.
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He also complained to Kejriwal about AAP's Punjab in- charge and senior leader, Sanjay Singh, who is considered to be extremely close to the Delhi chief minister, they said.
Incidentally, the move also comes at a time when the party MPs have questioned the central leadership's decision of appointing observers for the 13 Lok Sabha seats in Punjab without consulting them.
Following this, the MPs were also asked about the work done by them in their constituencies.
Although the party suffered a drubbing everywhere in the country, including in Delhi, it managed to win four Lok Sabha seats in Punjab in its maiden parliamentary poll outing.