John Singleton has called on Andrew Johns to "man up" and tell the truth to the More Joyous inquiry.

The former rugby league great had been "weak" over his part in the public stoush which shattered the relationship between Singleton and his former trainer Gai Waterhouse, the high profile businessman told the Network 7 on Tuesday.

On April 27, the day More Joyous finished second last in the All Aged Stakes at Randwick, the thoroughbred's owner publicly sacked Gai Waterhouse as his trainer saying he had been told her bookmaker son Tom had information the horse could not win, information he received from Johns.

"If I found out that Andrew Johns, who I have a high regard for as has the whole Australian sporting community, has rung up and told me a lot of nonsense and has done damage not only to Gai and myself but to Tom and Robbie (Waterhouse), I'll apologise to anyone who was hurt by it," Singleton said.

"He owes me an apology. He needs to front up and man up.

"How can you be so strong on the field and so weak off it.

"If he embellished it he owes me an apology and I owe them (the Waterhouses) an apology.

"My respect for Andrew Johns has diminished massively."

Singleton gave the interview to Network 7 reporter Ben Damon, his nephew, after Monday's inquiry at which Johns, former jockey Allan Robinson and punter Eddie Hayson failed to appear after being named as central figures.

Both Johns and Robinson gave statements which stewards said they wanted to cross-examine. Hayson is the last link in the chain and has not tendered a statement nor has he yet agreed to appear.

If Hayson doesn't appear he could be warned off, the harshest penalty imposed in racing.

Robinson rang Singleton on race day to pass on that Johns had told him Tom Waterhouse believed More Joyous could not win.

Waterhouse denies the accusation and tensions boiled over at the inquiry on Monday with an agitated Gai Waterhouse accused Singleton of being a drunk, and more insultingly according to him, old.

The inquiry is likely to resume early next week.