Veterinarians will be compelled to appear at Racing NSW stewards inquiries under new licensing conditions.

Racing NSW introduced the rule on Wednesday with vets given until August 1 to lodge their licence applications.

The rule will be enforced despite opposition from the Veterinary Practitioners Board and the Equine Veterinary Association which say vets are already subject to regulation from their own bodies.

In the ongoing cobalt case involving Sydney trainer Sam Kavanagh, one vet from the Flemington Equine Centre has so far declined to give evidence to the NSW inquiry.

In Victoria, there is legislation which requires vets to attend stewards' inquiries in that state.

A statement from Racing NSW said licensing of vets was crucial to the integrity of racing, particularly in relation to the use of illegal substances.

"A vet's licence will not be suspended or revoked unless it has been found that there has been a serious breach of the Rules of Racing," Racing NSW said.

"A vet can appeal any decision of the Racing NSW stewards to the Appeals Panel which is a tribunal independent of the Racing NSW stewards.

"Veterinarians are persons whose daily activities attending to and treating horses directly affect the integrity of race meetings and the public interest as it relates to the horse racing industry."