Tory councillor Derek Wann, who has fronted anti-bullying campaigns on behalf of Angus Council was revealed to be the owner of the "(Lady Whistledown) AngusFreeofSNP" account.
The account, styled after the anonymous newsletter-writing gossip from Netflix series Bridgerton, was followed by some members of Angus Council before its deletion earlier this week.
Cllr Wann used the account to challenge members of the public who interacted with his public persona on Twitter, and dished out abuse aimed at female and opposition politicians, including one tweet where he branded First Minister Nicola Sturgeon a "******* ned".
He even turned his vitriol against his own region, poking fun at the town of Brechin on several occasions.
The Arbroath East and Lunan councillor has admitted to being behind the anonymous account.
The SNP has challenged Mr Ross to take disciplinary action against the councillor.
SNP MSP Rona Mackay said: “There is no place in politics for such obnoxious and sleekit behaviour. Derek Wann’s conduct is absolutely indefensible, particularly in mocking drugs deaths.
“This is a serious test of Mr Ross’s leadership – he must act without delay. There is no need for an investigation when the man at the centre of it all has already admitted his atrocious behaviour."
Cllr Beth Whiteside, SNP group leader at Angus Council, said Mr Wann’s position was "completely untenable".
She said: "Cllr Derek Wann reveals his Jekyll and Hyde personality, with the revelation that he is the man behind the poisonous 'Lady Whistledown' Twitter account.
"The Angus Council senior councillor and convener of the children and learning committee, who has publicly pledged support for the 'ThinkB4UType' anti-bullying campaign, reveals himself to be nothing more than an anonymous online troll.
"Surely his position is now completely untenable."
Ben Lawrie, Liberal Democrat councillor for Carnoustie, said: "The unmasking of Lady Whistledown as a senior administration figure further illustrates the unhealthy culture at the top of Angus Council.
"Cllr Wann’s position as convener of children and learning is no longer tenable. He must resign."
However, Cllr Wann appears to have retained the full confidence of Angus Council leader David Fairweather, who followed and interacted with the anonymous account. It is not known whether he was aware of the true identity of the account holder.
Cllr Fairweather said: "Cllr Wann is a Conservative member and as such this will be investigated by that party.
"I have had a conversation with Cllr Wann and that will remain private.”
Cllr Wann accidentally exposed himself as the owner of the account when it posted a link to a press release on the Angus Council website in which he was quoted, and captioned the link: "My comments."
While the account has been removed, many of the tweets remain accessible via the Internet Archive. The Scottish Conservatives have launched an investigation.
Cllr Wann has not responded to a request for comment.