Calls by Andrew "Twiggy" Forrest for Australia's biggest iron ore miners to cap production are being investigated by the competition watchdog amid concerns about potential cartel behaviour.

Australian Competition and Consumer Commission chairman Rod Sims is urging the Fortescue Metals chairman to explain his comments, which may have breached the law in relation to cartel conduct. “The ACCC will be looking closely at Mr Forrest’s comments,” Mr Sims said. “Cartel conduct, anti-competitive agreements, price fixing and attempts…