Threats were made to a Dun Laoghaire-Rathdown County Council employee and their family over work relating to the Active Travel initiative.
The threats were reported to gardai and the council said they are treating it as a "serious incident".
Director of Dun Laoghaire-Rathdown County Council Robert Burns posted about the threats on Twitter.
He said: "A member of my project team recently received threats of harm against them & their family for work related to active travel.
"Sickening act & reported to Gardaí. Public discourse that seeks to undermine & breed mistrust in work of diligent public servants has a corrosive effect."
Cllr Peter O'Brien said "attacks like this are disgusting".
He tweeted: "This is sicking to read. Staff in @dlrcc have always made themselves available to meet residents and community groups.
"They are diligent, professional & committed public servants. Attacks like this are disgusting & have no place in a democracy."
Cllr Séafra Ó Faoláin posted: "The jump from insults to threats to intimidation to harm is less than we think. Some public reps have tacitly endorsed these insults.
"I hope the Council official and their family are recovering and that the perpetrator faces consequences."
A council spokesperson told Dublin Live: " In recent weeks, threats were made to a Dún Laoghaire-Rathdown County Council staff member and their family.
"This is being treated as a serious incident by DLRCC and the matter has been reported to Gardaí.
"DLRCC will not be commenting further at this time."
Dublin Live has contacted An Garda Siochana for comment.
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