TORONTO — The Competition Bureau is pushing for changes in how much Canadians pay in realty commissions after an investigation found the country's largest realtor association was operating with anti-competitive rules.

The decision could open the market to cheaper listing alternatives or result in lower listing charges on the Multiple Listing Service, or MLS.

An internal memo from Ottawa-based Canadian Real Estate Association to its members said that the federal bureau has told them its rules block competition within the industry, and that it has recommended changes.

"The bureau is concerned that CREA's rules have restricted consumer choice and limited the scope of alternative business models," according to a memo signed by CREA president Dale Ripplinger.

"The bureau's position is that if CREA does not remove these restrictions, the Commissioner of Competition will initiate an application before the Competition Tribunal."

The investigation follows complaints over how much consumers were paying in commissions to sell their homes, and the services they were charged to use.

"We have received complaints from realtors and they're arguing that the CREA restrictions require consumers to pay for services they don't want or need," said Greg Scott, a spokesman for the Competition Bureau.

The letter was sent out after CREA and the bureau met on Oct. 23 to discuss an investigation that has been underway since 2007.

A spokeswoman for CREA declined to comment on the investigation while the association is "negotiating" with the bureau on the situation.

CREA represents most of the country's real estate brokers and salespeople, and has more than 96,000 members across the country. Its MLS and Realtor.ca websites are home to most real estate transactions in Canada.