The future of media ownership limits was on Monday firmly placed back in the hands of the US Federal Communications Commission and Kevin Martin, the regulator's new chairman, after the Supreme Court declined to take a case that challenged the constitutionality of ownership rules.

The decision by the court, which had been widely expected to reject the case, marks a new beginning in the long-running and controversial debate about how big companies such as Rupert Murdoch's News Corporation and Tribune, owner of the Los Angeles Times, should be allowed to become.