Another unscheduled stable visit by Victorian stewards has caught a trainer performing a procedure on a horse during the prohibited period before it raced.

Trainer Brett Scott admitted he had stomach-tubed Red Colossus during the 24 hours before it was due to race at Mornington on Thursday.

A Racing Victoria compliance steward visited Scott's Mornington stables at around 5.30 on Wednesday afternoon.

Red Colossus had been due to race in the Lord Stakes at Mornington at 4pm on Thursday.

Under the rules of racing no treatment can be administered during the 24 hours prior to a race.

Scott pleaded guilty and was fined $1000 and Red Colossus was withdrawn from the race.