Tony Abbott is grilled by 7.30 host Leigh Sales over comments about the BHP Olympic Dam mine project

THE ABC has been cleared of accusations of bias over one of television presenter Leigh Sales' interviews with Opposition Leader Tony Abbott.

In a decision published today, the Australian Communications and Media Authority (ACMA) found the broadcaster did not breach its own impartiality code during the 7.30 program on August 22.

Leigh Sales' questions led the opposition leader to the embarrassing admission he hadn't read statements by BHP Billiton on why it suspended its Olympic Dam project, after he had blamed the carbon tax for the stoppage.

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The interview caused a stir on Twitter and Mr Abbott was forced to defend himself in parliament the following day.

ACMA received two letters complaining of bias by Ms Sales.

One said her treatment of Mr Abbott was "very bad'' and "she made it very obvious that she does not like him and is a Gillard supporter''.

The other said Ms Sales' "left-wing views'' showed through in her interviews.

In a response to the ACMA, the ABC said Ms Sales had used a "devil's advocate'' style of interviewing.

"We do not believe that posing testing questions to an interviewee and then allowing them to respond to those questions is biased or bad mannered,'' the ABC wrote.

"It is in fact a recognised standard of objective journalism.''

In its decision, the ACMA said Ms Sales used a "robust'' questioning style but Mr Abbott had been given a fair chance to respond.

The presenter "demonstrated an element of scepticism'' but the questions were reasonable given Mr Abbott's own statements, the authority said.

"The ACMA does not consider that the presenter conveyed a pre-judgment about Mr Abbott ... rather, she presented to Mr Abbott material suggesting what appeared to be differences between current events and his public statements and asked him to respond, thereby permitting viewers to evaluate the issues raised.''