A police investigation is underway after a political staffer applied for an apprehended violence order (AVO) against New South Wales Labor Party general-secretary Jamie Clements.

The AVO relates to an allegation that Mr Clements tried to kiss staffer and former Labor candidate Stefanie Jones in an office at state parliament in June.

A statement from New South Wales Police said they were investigating an assault allegation.

"Police from the Sydney City Local Area Command are conducting inquiries into the alleged assault of a woman within a room at Parliament House in June 2015," the statement said.

"As the matter is the subject of a current investigation, no further comment can be provided."

It is understood Mr Clements, who is a married father of three, and Ms Jones had a relationship in 2013.

Ms Jones is now engaged to Labor state organiser David Latham.

A source close to Mr Clements told the ABC that Mr Clements "denies any wrongdoing and will vigorously defend the allegations."

The parliamentary pass for Mr Clements was cut on Tuesday at the request of the Opposition Leader's office.

A spokeswoman for Opposition Leader Luke Foley said the office had referred the matter to the NSW branch president.

"A matter was raised with the office of the Leader of the Opposition pertaining to an electoral officer of the NSW Parliament," she said.

"The office has liaised with the Department of Parliamentary Services to ensure the welfare of the staff member in question, and [to] ensure she receives the appropriate support.

"The Leader of the Opposition has also referred this matter to the president of the NSW branch of the Labor Party.

"The matter is now subject to a police investigation, and as such it would be inappropriate to comment further."

Mr Clements has taken leave to fight the allegations.