The simmering feud between Gai Waterhouse and John Singleton boiled over at Randwick on Saturday with the high-profile businessman removing his horses from the trainer's stable.

Singleton teed off after eight-time Group One winner More Joyous beat just one runner home in the All Aged Stakes, won by All Too Hard.

He alleged he had received reports Waterhouse's bookmaker son Tom had told people all was not well with More Joyous.

"Tom has been saying she has got problems and I don't know about them," Singleton told the Seven Network.

"It's too much. It's a conflict of interest.

"Tomorrow my horses will be moved to another trainer. When I hear the horse has got problems and I don't know about it, it's wrong."

His public comments prompted a stewards' inquiry, where Waterhouse said the mare had been treated with an antibiotic on Thursday for heat in her neck, a problem Singleton's vet John Peatfield and stable vet Leanne Begg considered minor.

Peatfield examined the horse on Saturday morning and said she was fit to race.

Singleton was asked to name the source of his information about Tom Waterhouse.

"If I'm legally obligated I will do that, but I'm not prepared to give them up," he told stewards.

"It is an embarrassment to them. They told me not to back the horse.

"All my horses are leaving the stable tomorrow."

Chief steward Ray Murrihy said stewards could not act on rumour.

"We cannot put much weight on racecourse tattle," he said.

"Millions of dollars are being invested on the race and we need to get to the bottom of this and find out if Tom Waterhouse is being misrepresented in this."

Waterhouse and Singleton fell out when Waterhouse chose barrier 11 for More Joyous in the Cox Plate in which the mare finished 11th of 14.

Described at the time by the pair as a lovers' tiff, the rift has worsened over recent months, with several of Singleton's horses transferred to other trainers.

Asked outside the inquiry if she had any comment, a visibly upset but dignified Waterhouse said, "No. Nothing."

Singleton said he had no thoughts of retiring More Joyous and would continue to race her into the autumn.

The inquiry was adjourned until next Friday.

Waterhouse's bookmaker husband Robbie tried to talk to Singleton as he left but was given the brush-off.

The controversial incident capped a bad Randwick carnival for Gai Waterhouse, who went through the three weeks without a Group One winner.

Tom Waterhouse later used Twitter to say he had backed More Joyous and lost.

"I backed More Joyous today and as you can see All Too Hard was a strip out," he said.