A total ban on anabolic steroids in racehorses in and out of competition in Australia will come into effect next year.

The Australian Racing Board (ARB) announced a zero tolerance policy on Monday, saying there would be heavy penalties for any breaches of the new rule.

The ARB said the only exception to the rule would be for foals up to the age of six months in the interests of animal welfare.

Under existing rules, anabolic steroids are only prohibited in horses on race day but the new ban will apply to all thoroughbreds from the age of six months.

"The ARB has adopted a zero tolerance policy to the use of anabolic steroids in competition, training and spelling and will institute heavy penalties for breaches of the ban," ARB chief executive Peter McGauran said.

"Foremost in the board's consideration was the need for absolute integrity and public confidence in racing.

"Although the use of steroids has greatly diminished over the years to the point where they are rarely relied upon by trainers, the ARB believes it is in the best interests of the industry that they no longer be available for any purpose other than as a therapeutic treatment for young foals.

"Racing is a sport and as such must be a test of the ability of the individual horse, its trainer and rider and not of the pharmacologist, veterinarian or sports scientist. The true spirit of competition means that no-one gets an unfair advantage which anabolic steroids can confer in certain situations."

Anabolic steroids promote protein synthesis, muscle growth, red blood cell production, tissue repair after stress and injury and appetite to meet demands for additional nutrition.

"The ban on anabolic steroids goes far beyond any other racing jurisdiction outside of Europe and was decided by the ARB Board after lengthy consideration of veterinary and scientific advice and consultation with trainers' and owners' associations," McGauran said.

The new rule will be introduced from November 1 with the ban taking effect from May 1, 2014 giving six months for a horse to be free of any steroids.