The lawyer acting for Catherine Marriott has expressed disappointment the Nationals are yet to finalise a response to a complaint of alleged sexual harassment against former deputy prime minister Barnaby Joyce.

Ms Marriott, who was outed in the media despite wishing to remain anonymous, lodged a complaint with the Nationals about Mr Joyce's behaviour.

It was made public in February.

Mr Joyce has repeatedly denied any wrongdoing and has also called for the inquiry to be finalised.

"I believe a conclusion is imminent," Mr Joyce said today.

The lawyer acting for Ms Marriott, Emma Salerno, provided a statement to the ABC.

"We are extremely disappointed with the timeframe for resolving this matter," the statement said.

"Delay only exacerbates the stress on all parties to a complaint and we have not been given any indication by the Nationals as to when they intend to determine the matter."

In March, Ms Marriott hit back at suggestions there was a political motivation behind her complaint.

"Speculation on this issue by people who are unaware of the facts is impacting my right to fair and due process," she said at the time.

"The additional stress of having to go through this publicly and with people's judgement is the exact reason people don't come forward."

Mr Joyce resigned as deputy prime minister after the complaint and following the revelations he and former staffer Vicki Campion were having a baby after starting an affair while she worked in his office.

The complaint is being handled by the New South Wales branch of the Nationals and they have been approached for comment.