Fine Gael Senator Catherine Noone is standing over claims of bullying and sexism she has made against another party member.
She made the allegations at a private meeting of party TDs and senators in Leinster House last night.
Taoiseach Leo Varadkar committed to fully investigating the claims, saying sexism had no place in the party.
It is understood Senator Noone’s intervention at the meeting followed a presentation about the party’s efforts to encourage more women to contest elections for Fine Gael.
The allegations date back several years, but Senator Noone claims the alleged bullying has intensified since the debate around the referendum on the Eighth Amendment got under way.
Catherine Noone chaired the all-party Oireachtas Committee that examined the Eighth Amendment last year.
The senator has declined to comment publicly on on the allegations.
In a statement, Fine Gael said: "Parliamentary Party Chairman Martin Heydon has written to General Secretary Tom Curran regarding an internal matter within the party.
"Due process will be followed and the matter will be dealt with swiftly.
"Fine Gael expects party colleagues to treat all with the utmost respect, professionalism and dignity at all times.
Any internal party matters are dealt with the strictest of confidence and Fine Gael will not be making any further comment".