Trainer Darren Smith has been banned for 15-years by Racing NSW Stewards on Friday for 42 charges relating to cobalt use. 

Racing NSW Stewards say Smith had purchased a product from disqualified Harness Racing identity Shannon Wonson and embarked on an admitted course of conduct to inject multiple horses in his stable. 

The Newcastle trainer admitted injecting horses with a substance given to him by a disqualified harness racing trainer and which he understood to be a blood booster, after initially denying he had administered cobalt. 

Stewards handed down the heavy penalty citing Smith's previous poor record of drug-related offences.

It was Smith's tenth offence regarding prohibited substances since 1989.

Earlier this month Stewards found Smith guilty on charges relating to 21 positive samples. He had been charged under three different rules for each of the offences, but after finding him guilty of two, found it was unnecessary to rule on the third.

A total of 17 runners from 20 race starts returned positive samples for cobalt for races between February and May in 2014.