Monaghan Councillor Cathy Bennett is to be investigated by Sinn Féin after travelling to Lanzarote for a family holiday.
Councillor Bennett and her family spent 10 days in Lanzarote, against Government advice not to travel unless necessary.
Spain remains off the Irish government's green list, meaning anyone returning from the country or its islands must quarantine for 14 days.
In a statement to Northern Sound News at the weekend, Councillor Bennett apologised and said she and her family had restricted their movements on their return to Ireland.
It’s understood they stayed at a family holiday home in Rossnowlagh in Co Donegal before returning to Monaghan.
However, a Donegal TD says he’s furious Councillor Bennett chose to self-isolate in the county.
Sinn Féin TD and the party’s Chief Whip Padraig MacLochlainn told Highland Radio the matter will be investigated.
Meanwhile, Independent Councillor in Monaghan Paudge Connolly is yet to comment after it emerged he broke quarantine guidelines to attend the Oireachtas Golf Society event in Galway last week.
In an interview with The Joe Finnegan Show, the former Cavan-Monaghan TD confirmed his attendance but it subsequently emerged he had broken the quarantine guidelines.
He had taken part in a golf tournament in Alicante eight days before he travelled to Galway.
He is yet to respond to a request for comment, despite widespread calls for his resignation.
