THE broadcasting watchdog has dismissed allegations that 7.30 host Leigh Sales showed bias against Opposition Leader Tony Abbott.

The Australian Communications and Media Authority investigated the interview, aired on August 22, in which Sales grilled Mr Abbott over his claim that BHP had suspended its Olympic Dam project because of the carbon tax.

Ms Sales extracted an admission from Mr Abbott that he had not read BHP's statement, which made no mention of the tax.

The timing could not be worse for the Opposition Leader, who is now under attack for failing to read a Federal Court judgment dismissing the sexual harassment case against the former the parliamentary Speaker, Peter Slipper.