New South Wales Police Commissioner Mick Fuller refused to investigate allegations of homophobic bullying against four gay police officers before he took the top job, a Sydney tribunal has heard.

A hearing into alleged discrimination against the men has resumed in the NSW Civil and Administrative Tribunal.

Three serving officers, Chris Sheehy, Steven Rapisarda, Shane Housego, and former officer Christian McDonald are seeking compensation and an apology for their treatment.

Today, the tribunal heard that between March and May 2016, lawyers for the officers wrote to NSW Police, urging them to investigate the alleged homophobia.

The lawyers said the officers were targeted by a six-month professional standards command internal inquiry into drug use because of their sexuality.

But in a letter replying to the men's lawyers, then-assistant commissioner Fuller decided an investigation into the homophobia claims was not needed.

Ultimately the investigation cleared the men.

(L-R) Steven Rapisarda, Chris Sheehy and Shane Housego allege they were drug tested due to homophobia within the force. ( ABC News: Jason Om )

Lawyers for the men argued assistant commissioner Fuller "turned a blind eye" by rejecting their "series of pleas" to investigate.

Commissioner satisfied matter had 'full oversight'

Commissioner Fuller said in statement that he had "zero tolerance for any form of discrimination".

"A Professional Standards Command investigation was undertaken to resolve this issue and subsequently cleared all four officers. I was satisfied with this given the matter had the full oversight of the Ombudsman," he said.

"The NSW Police Force can make limited comment on matters before the courts and matters that are subject to ongoing investigation. However in all matters where complaints are made, they are taken seriously, investigated thoroughly by the NSW Police Force and examined by our oversight bodies."

Officers' superior made the drug complaint

The tribunal also lifted the secrecy around the source of a complaint which prompted the internal drug investigation as their superior, Superintendent Simon Hardman.

Superintendent Hardman authored the document, arguing the men's attendance at a gay venue, "loose morals and promiscuity" justified carrying out random drug testing on the officers.

The men alleged his actions were false and malicious and part of homophobic bullying culture at Newtown Police Station.