Regulators also halted Fairfax Media from selling nine regional radio stations to Macquarie Media for AUD $40 million Tuesday over concerns about the deal.

In contracts between the Courier and real estate agents, the agents agreed to place 75 percent of their print display real estate ads for properties in its circulation area with the paper, and in exchange received discounted advertising rates. The Courrier has offered these contracts since 1993, when the ACCC accepted the terms of a notification, according to The Australian.

In April, the Courier was bought by News Limited (which publishes The Australian), after it took over the Federal Publishing Company (FPC).

ACCC Chairman Graeme Samuel Tuesday said that although it is “not uncommon” for publishers to give volume-based rebates to advertisers, the Courier's contracts took the rebates too far, preventing “real estate agents from placing more than 25 percent of relevant advertising with competing publications.”

Samuel also said the rebate's requirement “also severely restricts the ability of Sydney daily newspapers, such as the Domain East insert in The Sydney Morning Herald, to compete for this business.”

Greg Baxter, News Limited's head of corporate affairs, said that although the contract terms have been in place since 1993 and were approved by the ACCC, and were inherited by the group when it acquired the FPC, the group “will work though any issues with the ACCC to achieve the desired outcome.”