The federal Competition Bureau is investigating whether recent moves to limit access to the Multiple Listing Service (MLS) are anti-competitive.

"I can confirm that the Competition Bureau is opening an inquiry into whether the MLS rules are raising competition concerns under the Competition Act," bureau spokesperson Marylyne Nahum told CBC News Online Monday.

The Competition Bureau says the MLS system is used in 90 per cent of Canadian real estate transactions.

The formal inquiry is targeting the possible violation of the act's provisions dealing with conspiracy and the "abuse of dominant position."    

The Canadian Real Estate Association (CREA) said Monday its current MLS policies and new interpretations comply with current competition and trademark law.

"Members of the Canadian Real Estate Association, which owns the MLS trademark, have passed seven interpretations designed to clarify how existing MLS rules are applied," association spokesman Bob Linney told CBC News. "The interpretations deal with requirements for anyone wanting to use the MLS trademark."

In the past, discount brokers have charged that CREA has been trying to squeeze out the discounters, who do most of their business online. CREA says it merely wants to protect the association’s MLS trademark.

The Competition Bureau said it has obtained a court order that requires the real estate association to produce documents relating to its MLS rules.

In an affidavit, the bureau said information from the industry indicated that about 90 per cent of residential real estate transactions in Canada involve the MLS database.

Last November, Realtysellers Ltd. suspended operations, "pending resolution" of the MLS trademark dispute.

Realtysellers is a Toronto-based company that gave rebates to buyers and sellers who used its services. It also advertised a $695 listing fee for private sellers who want their home on the MLS.

The Canadian Real Estate Association represents 88,000 realtors across Canada in 99 real estate boards.