A New South Wales Liberal MP has been expelled from the state division after a confidential complaint, that accused him of sending expletive-laden text messages to a female federal party figure, was upheld.

Taylor Martin stood aside from the party room last year after the woman, who he had been in a relationship with, lodged a formal complaint.

The ABC understands the allegations stem from when Mr Martin worked as a staffer in federal parliament years ago and that the complainant was a woman in the party.

In a statement on Friday evening, NSW Liberal Party State Director Richard Shields said the report from the independent investigation into the confidential complaint had been handed down.

And based on the findings, Mr Shields said he had acted “quickly and decisively, ratified by the State Executive, to expel Mr Martin”.

“And will continue to strive to ensure those standards are consistently upheld.”

Last year, the party appointed a senior counsel to undertake the independent investigation.

“I was young and inexperienced and I found myself involved in a situation that was way beyond me,” Mr Martin said at the time.

He also apologised saying the end of the relationship had been “an ugly and undignified parting of ways”.

Mr Martin has sat in the NSW upper house since 2017 when he was chosen to replace former police minister Mike Gallacher, who resigned from parliament.

His expulsion means he could sit as an independent on the crossbench, with his eight-year term due to expire in 2027.

Opposition leader Mark Speakman said he supports the decision.

“I support the NSW Liberal Party state director’s decision, made after a lengthy, independent investigation, to expel Mr Martin from the Liberal Party,” he said.

“Mr Martin is therefore no longer a member of the parliamentary Liberal Party.

“I expect, and the public are entitled to expect, the highest standards of behaviour by MPs.”

Mr Martin has been contacted for comment.