Australian Prime Minister Kevin Rudd was accused of using outdated slang to win over voters, after repeatedly demanding a "fair shake of the sauce bottle, mate".

The bookish and bespectacled prime minister used the phrase three times in a short interview with Sky News on Tuesday, each time accompanied by a self-conscious grin.

"We've appointed the first woman as governor-general of the Commonwealth of Australia -- fair shake of the sauce bottle, mate," Rudd smirked, when grilled about whether his government had done enough to promote women.

Opposition front-bencher Tony Abbott said Rudd was "desperate" to shake off his nerdy image and connect with the Australian people -- but was using language that was at least 30 years out of date.

"He's doing it in ways that don't sound authentic and that's a big problem," Abbott told reporters, dismissing the prime minister's "dated slang."

It is not the first time Rudd -- a former diplomat who was criticised for using impenetrable bureaucratic jargon after his election 18 months ago -- has resorted to the language of the common people to make a point.

In March, he said on national television that the global financial crisis meant his government was facing a political "shit storm", before immediately rephrasing and apologising to viewers.

And last year, Rudd revealed he had to "drive the porcelain bus," or vomit, after catching a stomach bug that he initially blamed on eating "a dodgy dagwood dog" -- a battered saveloy sausage served on a stick.

University of Queensland communication specialist Ian Ward said Rudd's "sauce bottle" phrase sounded contrived and was probably prompted by research showing the public thought he was out of touch with ordinary people.

"Kevin Rudd as prime minister has been constantly criticised by journalists and others for being a policy wonk and using long and complicated sentences and answering questions in convoluted and boring ways," Ward told the Australian Broadcasting Corporation.

"So he probably does have a problem cutting through," he added, suggesting Rudd wanted to appear more populist as an election looms next year.