Champion trainer Chris Waller has appealed the severity of a $30,000 fine handed to him after a horse from his stable tested positive for methylamphetamine.

Betcha Thinking returned a positive result for the drug known as ice after running second at Canterbury on October 5 but the source of the horse's contamination remained a mystery.

While stewards did not blame Waller at an inquiry on Friday they wanted to send a message with the hefty fine and were critical of security measures in his stable.

Stewards and Waller conducted drug tests on the stable's staff but agreed the one person who tested positive to methylamphetamine was unlikely to have come in contact with Betcha Thinking.

A date is yet to be set for Waller's appeal hearing.