Former Parliamentary Secretary for the Hunter Taylor Martin has apologised for "ugly and undignified" behaviour and excused himself from the Liberal party room after emerging at the centre of a complaint.
The Liberal party has appointed a senior counsel to independently investigate a formal complaint it received. The Daily Telegraph reported a woman made the complaint about alleged abusive text messages over a number of years.
The MP and the complainant were previously in a relationship.
"I was young and inexperienced and I found myself involved in a situation that was way beyond me," Mr Martin said.
"There were heated words during my attempts to go separate ways that I sincerely regret.
"It was an ugly and undignified parting of ways.
"If I could undo any hurt that has been caused I would do it in a heartbeat.
"I am so sorry and apologise unreservedly to everyone that has been caught up in it.
"I truly welcome the process that the party has commenced and I intend to fully cooperate."
Mr Martin's Facebook and Twitter pages appear to no longer be active.
Liberal leader Mark Speakman said he had spoken with the MP, who will excuse himself from the party room for the time being.
A Liberal spokesperson said the party has provided "relevant support".
"At all times, the party has respected the agency and wishes of the person who has come forward," the spokesperson said.
"The matter is being treated confidentially, and the party will not be making any further comment while the independent investigation is taking place."