The Tánaiste has said there is a "real problem" with the Fine Gael senator on the party's ticket following a 2018 incident.
Micheál Martin has objected to Fine Gael's decision to allow candidate John McGahon to run in the General Election.
Mr McGahon was accused of physically assaulting Breen White in an incident outside a Louth pub in 2018.
The Co. Louth candidate was cleared of a charge of assault by the Dundalk Circuit Court in 2022, however, he was found liable in a civil case and ordered to pay Mr White €39,000 in damages.
Yesterday, The Sunday Times published photographs of the damage inflicted on Mr White.
On, Let Me Explain with Seán Defoe, the Fianna Fáil leader said it is a "real problem" that Mr McGahon is running for election.
"I think the nature of the attack seems to have been very aggressive to say the least," Mr Martin said.
"The injuries are shocking and I think people can see, unfortunately online, the nature of the attack."
Taoiseach Simon Harris is continuing to support his candidate.
Sinn Féin leader Mary Lou McDonald said it is "shocking" to hear Mr Harris "dismiss questions" about Mr McGahon.
In a post on X, she said: "The photographs published this morning make it clear this was not a 'scuffle', as claimed by Simon Harris, but a very violent incident."
Deputy McDonald said Mr Harris needs to "make clear" how Fine Gael can "continue to support" Mr McGahon.
Shocking to hear Simon Harris dismiss questions about Fine Gael candidate Senator John McGahon.
The photographs published this morning make it clear this was not a ‘scuffle’, as claimed by Simon Harris, but a very violent incident. @SimonHarrisTD needs to make clear what if…
— Mary Lou McDonald (@MaryLouMcDonald) November 17, 2024
You can listen to Let Me Explain with Seán Defore right here.
Feature image: Micheál Martin at a launch of Fianna Fáil's manifesto in Smock Alley Dublin as part of the general election campaign. Photo: Leah Farrell/© RollingNews.ie