John Singleton could face conduct charges over allegations he made against bookmaker Tom Waterhouse over the running of his horse More Joyous at Randwick on Saturday.

Singleton launched an extraordinary public attack on Waterhouse after More Joyous finished seventh in the All Aged Stakes, saying the bookmaker had told people before the race the mare had problems and could not win.

He also sacked Waterhouse's mother, Gai Waterhouse, as his trainer and removed his horses from the stable on Sunday morning.

Tom Waterhouse has denied the accusations and will front the reconvened inquiry which has been moved from Friday to next Monday to enable stewards to gather all the betting information on the race and assemble the relevant parties including Singleton.

The Australian Rules of Racing provide for penalties for bringing racing into disrepute with AR 175A stating: "Any person bound by these Rules who either within a racecourse or elsewhere in the opinion of the Committee of any Club or the Stewards has been guilty of conduct prejudicial to the image, or interests, or welfare of racing may be penalised".

At the initial inquiry on Saturday, Singleton refused to divulge the names of "trusted friends" who had told him Tom Waterhouse was saying before the race there was a problem with More Joyous.

As a registered owner, he can be compelled to do so at the next stage of the inquiry.

"We cannot put much weight on racecourse tattle," chief steward Ray Murrihy told him.

"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."

A stewards' inquiry on Saturday heard evidence More Joyous had been treated with an antibiotic on Thursday after heat was found in her neck.

The inquiry also heard she had been passed fit to race by stable vet Leanne Begg and Singleton's vet John Peatfield.

The inquiry was originally opened to question the performance of More Joyous and escalated when stewards became aware of Singleton's on-course comments to the Seven Network and TVN.

"Tom has been saying she has got problems and I don't know about them," Singleton said.

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

"I was going to have $100,000 on her before I heard that."

Tom Waterhouse appeared on various media outlets on Sunday defending himself and his mother against the allegations by a former close family friend.

He produced a photograph of his ledger which indicated he backed More Joyous, who finished second last, and that the win by All Too Hard was a $300,000-plus worse result for him.

"All Too Hard was backed off the map. I laid All Too Hard till the cows came home," Waterhouse said.

"More Joyous is a 300-and-something-thousand dollar better result than All Too Hard."

Waterhouse also indicated he would seek legal advice about what he described in a press release on Saturday night as "totally inaccurate and untrue but also defamatory of me and also my mother".

Trainers are required to inform stewards if there are any issues with a horse that could affect its performance on race day.

Although Gai Waterhouse told stewards there was no issue with More Joyous, Murrihy said on Monday it would have been preferable if stewards had been informed so the Racing NSW vet could examine the horse.