Australia's newspaper regulator has intervened in a dispute over alleged bias by Rupert Murdoch's newspapers in the country's election campaign.
The watchdog told editors to provide an accurate account of public issues.
The Australian arm of Mr Murdoch's News Corp is the country's dominant newspaper publisher, responsible for around 70% of big city newspaper sales.
Prime Minister Kevin Rudd has accused Mr Murdoch's Australian newspapers of bias and of campaigning for a change of government at the 7 September elections, while Mr Murdoch has also used social media to press the demand.
Julian Disney, chairman of the Australian Press Council, has written to editors of major newspapers following complaints from the public and the industry over newspaper election reporting.
Mr Disney reminded editors of guidelines issued in 2009, which stress the need to distinguish news from editorial opinion.
However, the Press Council said newspapers have the right to hold a political opinion and favour particular candidates.
"Newspapers that profess to inform the community about its political and social affairs are under an obligation to present to the public a reasonably comprehensive and accurate account of public issues," Mr Disney wrote.
"As a result, the council believes that it is essential that a clear distinction be drawn between reporting the facts and stating opinion.
"A paper's editorial viewpoints and its advocacy of them must be kept separate from its news columns."
Mr Murdoch's top selling Sydney Daily Telegraph has run the strongest anti-government stories, with a front page headline on the first day of the election saying "Kick this mob out" over a photo of Mr Rudd.
Mr Rudd continued to criticise Mr Murdoch's newspapers today, urging voters to view an analysis of bias broadcast on Australian Broadcasting Corporation television last night.
The ABC's Media Watch programme said an analysis of the Daily Telegraph's reporting in the first week of the election campaign showed half of its 80 stories were slanted against the government, with none against the conservative opposition.
Over the next two weeks, it said, 59 stories were against the government, while only four were slanted against the opposition.
Just three stories have been slanted in favour of the government.
"I think it should be mandatory viewing across the country," Mr Rudd told reporters. "Because you know what is at stake there? It's the lifeblood of a democracy. It is about a fair contest of ideas. It's about a fair go for everybody."
The Australian Press Council is an industry body that rules on complaints against newspapers, but its findings are not legally binding and newspaper membership is voluntary.