Racing New South Wales says a judicial inquiry into the stoush between millionaire businessman John Singleton and the Waterhouse family would be a gross overreaction.

Federal independent Senator Nick Xenophon amid allegations trainer Gai Waterhouse passed on inside information to bookmaker son Tom about the state of Singleton's mare More Joyous.

Singleton .

Singleton says he was not aware of any issues with his star galloper, which started favourite in Saturday's Group One All Aged Stakes but faded for second-last.

Singleton and has reportedly begun moving his horses from Waterhouse's Randwick stables to his private farm north of Sydney.

Senator Xenophon says he will write to the NSW Government this morning to request a judicial inquiry into the matter.

"John Singleton's allegations are so serious this goes beyond the remit of a steward's inquiry," he said.

"The only way to get to the truth of this is to have an independent inquiry."

But Racing NSW says it is inappropriate and an attention-seeking move.

Chief executive officer Peter V'landys says the steward's inquiry should be able to continue this Friday without interference.

"Mr Xenophon should let due process take place and see the outcomes before making such outlandish statements," he said.

"We'll certainly vigorously pursue these allegations and make sure that people can have utter confidence in the racing industry in NSW."

Racing New South Wales chief steward Ray Murrihy said Singleton, along with the Waterhouses, will be required to appear when the inquiry continues on Friday.

Mr Murrihy said the initial inquiry was to investigate whether the poor performance from More Joyous was linked to a setback that the stewards should have been made aware of.

Gai Waterhouse continues to remain silent on the matter while Tom has protested his innocence.

"I back the horse and it was a $300,000 better result if it wins," he said.

"All Too Hard [the eventual race winner] took out 300-and-something-thousand - it was the worst result of the day for us."

He has met with his lawyers to consider a defamation lawsuit against Singleton.