At a meeting of Renfrewshire Council today, elected representatives from all parties backed a resolution calling for the ex-SNP minister to stand down from his Holyrood seat.
Mr Mackay, a former leader of the Paisley-based local authority, has not been seen in public since he shocked the Scottish political world with his sudden resignation from Nicola Sturgeon's cabinet on February 5 - just hours before he was due to deliver the 2020 draft budget to MSPs.
He has represented the Renfrewshire North and West seat since 2011.
The former finance secretary, 42, was revealed to have sent hundreds of messages to a 16-year-old boy via social media.
The teenager subsequently made a statement to Police Scotland but has not made a formal complaint regarding the behaviour of the politician, who has been suspended by the SNP but currently remains an MSP.
The motion was lodged by Labour group leader Eddie Devine and seconded by Councillor Jim Sharkey but passed with no opposition from SNP councillors.
Mr Sharkey was told he was “out of order” by Provost Lorraine Cameron when he hit out at the SNP group and asked them what they knew about Mr Mackay, the Paisley Daily Express reported.Councillor Sharkey said: “I think there is a serious issue and I think it’s how the SNP have treated a 16-year-old boy.
“What did you know about Derek? If you can’t answer 'nothing', you are not absolved from that.”
Provost Cameron interrupted Councillor Sharkey and said: “You are out of order. That is an outrageous slur.”
Independent councillor Paul Mack said today: “The people of Renfrew are paying for Mr Mackay’s actions. Mr Mackay has to come out of hiding right away. Derek has to go and he has to go now.”
Mr Mackay does not face arrest over the text message scandal which led to his dramatic fall from grace, police confirmed last week.
A police spokesman told The Scotsman: “We have not received any complaint of criminality, however, we are currently assessing available information.”
In allegations published earlier this month, Mr Mackay is said to have contacted the boy "out of the blue" and sent about 270 messages on Instagram and through Facebook.
In one of the exchanges it is claimed that Mr Mackay told the teenager he was "cute". In another the boy confirmed he was 16 and tells Mr Mackay "not to try anything".
Mr Mackay, who was widely tipped as a future first minister, came out as gay when he left his wife in 2013. He has not been seen in public since the scandal broke.