South Australian jockey Josh Cartwright has been suspended for 18 months over a ride at Morphettville that made national headlines when he steered his mount into two other runners.

The 22-year-old, who was recently granted a dual licence, also had his training licence suspended for six months.

Thoroughbred Racing South Australia chief steward Johan Petzer said in a statement Cartwright had expressed remorse following the incident and had fully co-operated with stewards at all times during their investigations.

"He has also been very open with stewards about a range of personal issues he felt contributed to his actions," Petzer said.

"The welfare of participants in racing is always our absolute priority, and stewards have provided access to professional counselling and support appropriate to the situation since January 14.

"Nevertheless, the panel felt that the degree of recklessness was in the extreme and that Josh Cartwright's riding in this race could best be described as abhorrent and, arguably, the worst ever seen in Australia.

"Given the need for the penalty to act as a deterrent to all riders and to protect the image of racing, we could not afford any leniency in terms of the penalty."

Cartwright was stood down immediately after pleading guilty to the reckless charge at Morphettville on January 14 when he rode Senior Council into two other horses.

Senior Council cannoned into Go The Journey and House Of Wax with the latter's jockey Jason Holder managing to regather and stay on his mount after almost falling..

The race at Morphettville was won by the $4 favourite Murti who was ridden by Cartwright's girlfriend, apprentice Anna Jordsjo.

Cartwright can ride trackwork on his own property and apply to return to general trackwork in six months time and in 12 months make further application to ride in jump-outs and trials.

While his trainer's license is suspended for six months, he is allowed to continue his activity as a horse breaker and pre-trainer.