South Australia-based Tommy Stokes has been fined for placing bets on his father's Victorian-trained horses to lose in a breach of betting rules.

Stokes, the son of Pakenham-based trainer Phillip Stokes, was fined $1500 by Racing Victoria stewards after placing seven "lay-bets" on his father's horses that raced in Victoria over a 2-1/2-year period.

A lay-bet is one where the punter backs a horse to lose.

The seven lay-bets resulted in a profit of $502 for Stokes.

Stokes, who is a stable employee of his father in South Australia, pleaded guilty to a charge of negligence in not understanding his obligations under the rules of racing.