The Fianna Fáil leader says the party was not aware that one of its general election candidates in Waterford had previously been disqualified from acting as a company director.
Cllr Eddie Mulligan was disqualified for seven years by the High Court in 2017 over the management of a family hair salon business.
According to The Irish Times, Cllr Mulligan was a director and shareholder of the company - which owed Revenue over €150,000 when it was placed in liquidation in 2014.
The general election candidate has been asked to provide an explanation to the party following the revelations.
Speaking this morning, Fianna Fáil leader Micheál Martin would not be drawn on whether the development could cost the councillor his election candidacy.
Mr Martin said: "We did not know about that, and we've asked him for a full explanation today.
"We've asked for a full explanation - I don't want to go any further than that at this stage."
