Bookmaker Tom Waterhouse will consider legal action against former family friend John Singleton over serious allegations he was aware More Joyous could not win at Randwick on Saturday.

Singleton publicly sacked Gai Waterhouse as his trainer after the race, saying he had been told by friends her son Tom was aware of a problem with More Joyous who finished second last in the Group One All Aged Stakes.

Tom Waterhouse denied Singleton's claims on various media outlets on Sunday before later tweeting he was seeking legal advice.

"Stunned and upset by Singo's comments regarding @GaiWaterhouse1 and me. They are completely false and wrong. I'm meeting with lawyers today," he said.

Racing NSW stewards opened an inquiry on Saturday into the performance of More Joyous before learning of the comments made by Singleton in on-course television interviews.

The inquiry then escalated with Singleton repeating the allegations but refusing to name his sources, saying he would only do so if there was a legal obligation.

In a pre-race interview Singleton flagged that he believed all was not well with More Joyous and launched a stinging attack afterwards.

"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.

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

Racing NSW chief steward Ray Murrihy said his panel could not act on rumour and were obliged to investigate Singleton's claims.

"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."

Gai Waterhouse told stewards More Joyous had been treated with an antibiotic on Thursday morning after she was found to have heat in her neck, something that was considered minor.

The mare was examined by stable vet Leanne Begg and Singleton's vet John Peatfield on Saturday morning and both declared her fit to run.

Singleton and Gai Waterhouse have had an uneasy alliance since the spring when the trainer went against his wishes and selected barrier 11 for More Joyous in the Cox Plate in which she was unplaced.

More Joyous, who Waterhouse has trained to eight Group One victories, has not won from three starts during the autumn.

Tom Waterhouse told TVN's Racing Review on Sunday he had backed More Joyous and All Too Hard was a major loss for him, producing a snapshot of his ledger.

"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 said he had not been called to the reconvened inquiry on Friday but Murrihy said he would be as soon as stewards could get in touch with him.