Champion trainer Chris Waller has been fined $1000 under a local rule of Queensland racing after one of his horses tested positive to a diuretic at the Gold Coast trials.

Stewards opened an inquiry into a urine sample which showed traces of furosemide after being taken from Invinzabeel at the Gold Coast on May 17.

Waller, who gave telephone evidence, pleaded guilty.

In a written report, released on Wednesday, stewards acknowledged Waller's forthright evidence that included his staff advising stewards immediately after the sample was taken the horse had been administered a product containing furosemide earlier in the morning.

Stewards also acknowledged that trainers in other Australian jurisdictions are permitted to trial horses with the aid of furosemide unless the horse is trialling to obtain a permit to race.

Waller was fined $1000.