Former Tennis Australia director Harold Mitchell has been fined $90,000 for breaching his directors' duties after a court case in which the Australian Securities and Investments Commission alleged he improperly helped the Seven Network secure the TV rights to the Australian Open over other networks.

The lengthy legal saga ended with a slap on the wrist for the advertising titan, with the $90,000 penalty falling well short of the maximum available fine of $600,000 for the three contraventions and, in a blow for the regulator, the $150,000 sought by ASIC.