Financial analysts have been querying the negative effects of real estate agents boycotting Trade Me and now the Commerce Commission has begun a probe.
Gordon Irving, commission spokesman, said the real estate ad situation was of interest to the organisation.
"I can confirm that the commission is investigating this issue. It is too early to determine the possible outcome of the investigation," he said.
Analysts have raised the issue, saying real estate is a major source of revenue for Trade Me so any change would negatively affect the business.
The NZ Herald has previously reported a group of real estate agents said they would boycott Trade Me after the company announced price rises.
Some vendors have complained about their properties not appearing on Trade Me, saying they wanted them listed there.
Trade Me chief executive Jon Macdonald said late last year that if Hamilton agents withdrew listings it would disadvantage property owners and that a listing fee of under $200 represented good value for money.
The commission enforces legislation that promotes competition and prohibits misleading and deceptive conduct by traders. It also enforces a number of pieces of legislation that, through regulation, aim to provide the benefits of competition in markets where effective competition does not exist.
This afternoon more than 20,000 properties were advertised for sale on Trade Me. Listings shown included Northland 5974, Auckland 9701, Waikato 6722, Bay Of Plenty 4932, Wellington 3968, Canterbury 5141 and Otago 4003.
Trade Me Group expects to release its preliminary financial results for the six months to December 31 on February 19. Its shares are trading around $3.85.