Former champion jump jockey John Francome says he believes about six horse races a year could be fixed.
Francome was speaking on the BBC's Sportsweek programme
Francome's comments come in the wake of former champion flat jockey Kieren Fallon being charged with conspiracy to defraud last week.
Asked if jockeys had cheated, Francome told Five Live's Sportsweek programme: "I guarantee that they have. It happens - it's life. Join the real world.
"I should think it happens about half-a-dozen times a year."
But Francome defended the sport, insisting the fact races were fixed so infrequently should be applauded.
"When you think how many races there are it's actually not a lot when you see players diving every two minutes in a football match - which is cheating just the same," he said on BBC Radio Five Live.
"Considering how many races are run, it's fantastic."
Francome also said it was very hard to prove whether or not a race had been fixed.
"It's very difficult," he insisted.
"You are talking about a jockey riding a horse and he comes back in and you say 'we don't think that you have tried as hard as you should' - and he says 'well hang on - there was something wrong with the horse'.
"Now, although I watch a horse and think the jockey hasn't done his best, actually you try to prove it - because horses aren't machines."
Francome believes extensive television coverage means there is less room for the cheats to prosper than there was previously.
"Every single race is televised. Years ago when there was no television at all then it was a lot easier to get away with things," he said.
"By and large, there's nothing to worry about. These are isolated cases.
"If you are a punter sitting at home I wouldn't worry too much."