Suspended trainer Ben Smith will face a further 10 charges following two Racing NSW inquiries into the use and supply of prohibitive substances.

The charges follow a protracted stewards' investigation that opened following the discovery of a brown bottle in Smith's car near the Newcastle racetrack in September.

Stewards initially laid two charges against Smith and suspended his licence after two horses he trained subsequently returned prohibited levels of cobalt from raceday swabs.

Iron Duke and Elaborate tested above the allowable threshold after their wins at Newcastle on August 25 and Wyong on August 26 respectively.

A preliminary analysis of the swabs sparked the stewards' inspection of Smith's Newcastle stable.

Smith was stood down when it was found he had given false evidence while refusing to reveal details relating to unlabelled and unidentifiable substances in the stable.

Smith came to prominence as the trainer of top sprinting mare In Her Time who rose the grades in 2017.

In Her Time confirmed her place among the ranks of Australia's best sprinters with her win in the Group One Galaxy during last year's Sydney carnival.

Two weeks later, Smith celebrated his second Group One success when El Dorado Dreaming came from near-last as an $81 chance to win the ATC Sires' Produce Stakes.

Both horses now race out of the Kris Lees stable following the suspension of Smith's licence.

The latest charges stem from Racing NSW inquiries in February and March.

Racing NSW said the 10 charges would be heard on May 7.