Ticketek has been hit with a $2.5 million fine for using its market power to engage in "opportunistic" and anti-competitive behaviour, the consumer watchdog says.

The Federal Court found yesterday that the ticketing giant had tried to prevent or deter another ticket business, Lasttix, from supplying its services on four separate occasions.

In 2009 and 2010, concert promoters and theatre producers had requested Ticketek set up special discount ticket deals through Lasttix for shows that included celebrities Dr Phil and Liza Minnelli, the Australian Competition and Consumer Commission said.

Despite agreeing to do so, Ticketek did not.

This was because the deals were going to be promoted by Lasttix, which offers last-minute tickets at a discounted price, the ACCC said.