Gerald Ryan has refused to comment on claims that he sexually assaulted controversial jockey Danny Nikolic 20 years ago. He has also been implicated in a series of other alleged assaults on young jockeys and stable hands at the Hobson's Lodge stables near Flemington in Melbourne, which belonged to racehorse owner and current Victorian Racing Club chairman David Moodie. No charges have ever been laid against Mr Ryan.

Aside from breaking these explosive allegations, a Fairfax Media investigation has found that when Queensland's racing administrator granted Mr Ryan a trainer's licence in 1997, it did so under the strict condition that he not be allowed to hire any male staff under the age of 21.

Today, he continues to train more than 100 horses from bases at Sydney's Rosehill and Queensland's Gold Coast.

In a statement released on Saturday, Racing NSW chief executive Peter V'landys confirmed the body was "thoroughly investigating the matters raised" in the Fairfax Media investigation, but he stressed "every person is entitled to due process and natural justice".

Mr V'landys added: "It would be inappropriate to make any further comment at this stage, other than to reiterate that Racing NSW takes any allegations of sexual assault or criminal activity very seriously and will investigate fully and take whatever action is warranted."

Prior to the alleged sexual assault of Nikolic, which is said to have occurred in a Sydney apartment after the jockey had fallen asleep, it is claimed that Mr Ryan abused former jockeys Jamie Evans and the late Mark Goring in 1986. Sources said a prominent Perth jockey was also sexually abused when he was an apprentice with Mr Ryan in Melbourne.

Following the ongoing accusations against Mr Ryan, Mr Moodie called a meeting of all staff at Hobson's Lodge in April 1996. According to reports at the time, Mr Moodie asked if anyone had been sexually harassed – and more than half of the 22 employees raised their hands.

Within days of the meeting, Mr Ryan went on a month's leave from Hobson's Lodge, while an investigation was launched by stewards from the Victoria Racing Club.

More than 30 people were interviewed during the course of the inquiry including 22 stable hands, six jockeys, three apprentice jockeys, and an owner believed to be Mr Moodie.

The VRC later notified Mr Ryan that he would have to "show cause" as to why he should keep his trainer's licence, at a hearing on June 6, 1996.

On June 3 – just three days before he was due to defend the serious accusations – Mr Ryan handed back his licence. At the time, he was Victoria's leading trainer, but did not explain his shock departure.

He is understood to have trained horses in Malaysia for a stint and then, in 1997, he returned to Australia and applied to run stables on the Gold Coast.

Internally, the Queensland Principal Club, now known as Racing Queensland, were divided about whether they should let him but were advised, legally, that because he had not been charged with any criminal offences they could not prevent him from obtaining a licence.

"It was not a very happy decision," said a former board member. "But our hands were tied."

Victoria Police have confirmed they interviewed a 61-year-old man from Parramatta in 2011 "in relation to a historical indecent assault" but no charges were laid and the case was closed.

With Eamonn Duff, Cameron Houston and Chris Vedelago