Fine Gael Councillor Kenneth Egan has resigned the party whip after he holidayed in west Cork a week after returning from a boxing event in the UK.
Mr Egan was coach for Kildare boxer Eric Donovan, who lost an IBF Super Featherweight Intercontinental title fight to Zelfa Barrett earlier this month.
Government guidelines require people to restrict their movements for 14 days after returning from the UK.
The Olympic boxing silver medalist has sincerely apologised for breaching the health guidelines earlier this month.
"It simply should not have happened. I made a big mistake and I am sincerely sorry for it.
"To defeat this pandemic, all should obey the public health guidelines. Public representatives have an even bigger responsibility to do so and I failed in this regard," the South Dublin County Councillor said.
Separately Social Democrat councillor for Kildare Bill Clear has been suspended from the party for six months after he went on a family holiday to Spain last month.
Like the UK, Spain is not on the Government's green list of countries deemed safe to travel to and anyone coming into Ireland from Spain must restrict their movements for 14 days.
Spain currently has the highest 14-day incidence of Covid-19 cases per 100,000 at 191.9.
The party’s national executive said Mr Clear accepts that he exercised poor judgement relating to the trip and that he has apologised to his constituents in Kildare and to his fellow councillors.
Mr Clear had already resigned as leas-cathaoirleach of the Naas Municipal District.
The executive said it took into consideration the seriousness of the issue, his expressions of regret, and the actions he has already taken to demonstrate that regret when making its decision.
The party also said Cllr Clear has been a strong representative for his constituents on Naas Municipal District.
Despite the loss of the party whip, Mr Clear said he will continue to represent his constituents on Kildare County Council during this period.
Meanwhile, Sinn Féin has confirmed it has withdrawn the party whip from Monaghan Councillor Cathy Bennett after she went on a family holiday to Lanzarote.
In a statement, Sinn Féin party whip in Monaghan Councillor Brian McKenna said Ms Bennett "breached party guidance and public health advice regarding international travel".
He says it is "vitally important that elected representatives show leadership in respecting the necessary public health advice so that we can collectively tackle Covid-19".
He said Ms Bennett will accept the sanction "in recognition of her mistake".
