The rebirth of one of the greatest ever tennis rivalries has helped Seven score a big ratings win overnight, but the network’s broadcast deal with Tennis Australia is reportedly under investigation.

According to the latest OzTam figures, Channel Seven’s broadcast of the Australian Open men’s final between Roger Federer and Rafael Nadal attracted over 2.6 million viewers across the five metro city markets, while the trophy presentation topped the most-watched programs list with an audience of over 2.7 million.

The ratings success saw Channel Seven pick up 50.6 per cent of audience market share last night, and push the Seven Network’s share up to 54.5 per cent.

Nine’s best-rating program overnight was its 6pm news bulletin, which attracted over 1.1 million viewers, while the season premiere of Ten’s I’m A Celebrity… Get Me Out Of Here also registered over 1.1 million viewers.

Overall audience market share for the two networks was at 17.9 per cent and 15.4 per cent respectively.

However, Seven’s ratings success could be soured by an investigation into the broadcast rights deal between Tennis Australia and Seven West Media.

According to Fairfax, the Australian Securities and Investments Commission (ASIC) is probing Tennis Australia over claims a conflict of interest involving businessman Harold Mitchell may have influenced the decision to sell the Australian Open TV to Seven West Media in 2013.

Fairfax revealed that Tennis Australia and Seven agreed to a five-year extension of the broadcast deal worth approximately $35 million annually without taking the rights to the open market.

It is understood that the deal created speculation from rival TV networks that Tennis Australia may have lost up to $50 million in potential revenue from the deal, while global sports group IMG has claimed its offer to pay $40 million annually for the rights was rejected.

According to Fairfax, ASIC is investigating how the possible conflict of interest was dealt with in the Tennis Australia boardroom. At the time of the deal, Mitchell was vice-president of the organisation and chairman of Aegis Asia Pacific, which had commercial dealings with Seven.