The South Sydney Rabbitohs have sacked star centre Kirisome Auva'a following a second breach of the NRL's illicit substance policy.

While Auva'a did not return a positive test, the league found he had "contravened the rules as set out in the NRL Policy".

Auva'a and the Rabbitohs opted against appealing the findings last week, with the club now exercising its right to terminate the player's contract.

In a short statement, South Sydney said it would "continue to offer welfare assistance and support to Kirisome", whose troubled career has also included domestic violence charges and struggles with mental illness.

Auva'a has become the second Rabbitohs player sacked this week after Paul Carter was let go for a contract breach on Tuesday.