Apprentice Mitch Aitken has been suspended from race riding for three months after returning a positive test to a banned substance.

Aitken, who has ridden 27 winners this season including six city winners in Victoria, was stood down from riding and handling horses by Racing Victoria stewards on June 9 when an irregularity in a urine sample taken from him during trackwork at Seymour on May 24 was first detected.

After the positive result was confirmed, Aitken pleaded guilty to a charge of providing a sample which contained a banned substance.

Stewards on Thursday issued the three-month suspension after taking into account Aitken's personal circumstances and guilty plea.

Aitken can ride trackwork and trials once he delivers a clean sample.

The suspension is backdated to begin from the day he was stood down and he can return to the races on October 9.