Kieren Fallon faces a Jockey Club inquiry after losing in controversial circumstances amid allegations of suspicious betting patterns.
Fallon was well clear on 15-8 shot Ballinger Ridge at Lingfield, but seemed to ease up a furlong out and lost by a short head to favourite Rye.
After a two-hour hearing, the stewards found the champion jockey guilty of failing to ride out for first place.
However Andrew Balding, the horse's trainer, defended Fallon's display.
"It looked worse than it was," said Balding.
"Kieren said he was giving our horse a breather and then was asking him to go again.
"The horse is a maiden after a lot of opportunities and is not the easiest of rides."
A deputation of about 100 angry punters gathered outside the weighing room and booed Fallon on his return.
The Jockey Club confirmed that unusual betting patterns had been reported before the race.
"Kieren Fallon has been referred on to the Jockey Club with the reason being
that shortly before the race, the security department contacted the Lingfield stewards to report what they describe as suspicious betting patterns," said Jockey Club spokesman John Maxse.
"In view of what happened in the race, it would be remiss of the stewards to resolve the matter on course without considering whether there is any correlation between the two."