Party sources familiar with the matter said they warned Mr Gray not to take the role on Ms Husar's campaign because they knew of her reputation. Mr Gray said he still regularly sees a therapist.

Ms Husar, who is currently on leave amid an internal investigation into allegations of bullying and misconduct, did not respond to a request for comment.

It is understood more than 200,000 words of evidence have been given to barrister John Whelan, a former Labor staffer appointed by the party to examine claims against Ms Husar.

But in a stunning development, Mr Gray said he had not been asked to give evidence to the inquiry, despite last year writing to NSW Labor secretary Kaila Murnain about his experience.

"I haven't been contacted at all," he said. "I don't understand how they haven't contacted me. People knew this was happening three years ago."

When Ms Husar was preselected for the seat of Lindsay, it took five months for the party to formally endorse her - an unusual delay understood to be due to issues arising from the state campaign.

Separately, a former staffer to Ms Husar who worked for her while she was a federal MP,  said the treatment alleged by Mr Gray was consistent with the way he and other staffers had been treated.

The ex-staffer said Ms Husar had "ridiculously high standards", would "make you do things outside your role as a professional" and was "rude and aggressive and intimidating and just cruel".

Mr Gray said he wrote to Ms Murnain last June about his experience on the campaign and his ideas to improve party processes, but did not receive a response. He said he has not given evidence to the Whelan investigation because he has not been approached and does not trust the process.

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A spokesperson for NSW Labor confirmed the party had received Mr Gray's letter by email, but it had not been opened "as the party was experiencing a large volume of correspondence at the time".

"The ALP has established an independent investigation of complaints and allegations against the Member for Lindsay," the spokesperson said.

"This correspondence has been referred to the investigation. Given how important these issues are, the delay in responding to Mr Gray's concerns are obviously regretted. We assure him his concerns will be addressed."

Mr Gray said he is still an ALP member but has stopped participating in party activities.

"I’ve been gradually withdrawing from Labor altogether," he said. “I still believe in Labor values and the Labor Party but I don’t feel that I can contribute or participate while [Ms Husar] is still involved."

About 20 former staffers have reportedly given evidence to the Whelan inquiry into Ms Husar, with claims she called staff "c--ts" and "f---wits", and made them do her domestic duties such as looking after her children and picking up after her dog.

Federal Labor leader Bill Shorten has maintained he was unaware of the investigation into Ms Husar until last week, when his office was contacted by BuzzFeed News, which broke the story.