Mr Shorten and his senior colleagues accused the media empire of being a "cheer squad" for Prime Minister Scott Morrison and cited its use of tax havens in the Cayman Islands as one reason it wanted to stop Labor taking power on May 18.

Labor deputy leader Tanya Plibersek said the company was trying to block funding increases for schools and hospitals while protecting "tax loopholes".

"I wonder if that's got anything to do with the fact that Rupert Murdoch and his companies pay little or no tax in Australia? It could be something to do with the fact that News [Corp] has paid very little tax in Australia in recent years," Ms Plibersek said.

The sharp criticism of Mr Murdoch's company and its tax affairs is seen as a warning shot in a deepening dispute after years of friction and negative stories about Labor throughout the campaign.

In an emotional address to the media that saw him come close to tears, Mr Shorten slammed the company's Sydney newspaper, The Daily Telegraph, for a report that used the headline "mother of invention" and suggested he had misled voters about his mother.

Mr Shorten attacked the newspaper for its "political hit" and "gotcha shit" and talked of his mother's attempt to get work as a barrister when she faced discrimination because of her age, leading him to promise to act on the problem if he became prime minister.

Labor assistant treasury spokesman Andrew Leigh said the "extraordinary attack" by The Daily Telegraph was no coincidence when News Corp could be hurt by plans to toughen laws on tax havens.

Mr Leigh cited reports from four years ago that News Corp had dealings in the Cayman Islands and was in the "highest risk" category at the Australian Taxation Office.

"I don't think it's any coincidence that when a party is taking to the election the most comprehensive set of policies on multinational tax reform, that we find ourselves under fire from News," Mr Leigh said.

The Australian Financial Review reported in May 2015 that the ATO had only one company in its highest risk category for tax avoidance and this was News Corp. A News Corp spokeswoman said there was no comment from the company.

Labor is promising to raise more tax revenue from a crackdown on tax havens and profit shifting by global companies, but the Coalition has also targeted these tax problems as well over the past six years, recouping billions of dollars.

Labor finance spokesman Jim Chalmers said the News Corp publications had made their position "very clear" but should not bring Mr Shorten's mother into their criticism of Labor.

"They go to any length to prop up the Liberals, to prop up a failing government, which has spent six years rotating through three prime ministers, which has doubled debt in this country, which has presided over slowing growth and stagnant wages," he said.

"This is what they do."

Former Labor prime minister Kevin Rudd backed Mr Shorten by comparing The Daily Telegraph to a newspaper run by a totalitarian dictatorship.

"Surprise, surprise!" Mr Rudd tweeted. "The Murdoch media launch a front page full-blown character attack on Shorten ten days out from election day. Fully coordinated with their coalition partners the Liberal Party. Today's People's Daily in Beijing is a more objective source of news."

The Daily Telegraph's report came after Mr Shorten ended his appearance on the ABC's Q&A program on Monday night by saying his mother had wanted to be a lawyer but needed to take a teacher's scholarship when young.

The front-page newspaper report, accompanied by two pages of coverage and an editorial, said Mr Shorten had omitted the fact that his mother had become a lawyer later in life.

Mr Shorten rejected the newspaper's coverage on Facebook before unleashing during a press conference in Nowra, where he was campaigning for the marginal seat of Gilmore.

"My mum is the smartest woman I've ever known," Mr Shorten said.

"Mum taught me it doesn't matter about your gender. It matters how hard you work. But everyone deserves the same chance."

Prime Minister Scott Morrison extended his "best wishes" to Mr Shorten when asked about the newspaper story, adding that he could understand the hurt it caused.

"This election is not about our families. It's not about Bill's mum. It's not about my mum," Mr Morrison said.

Disputing The Daily Telegraph's coverage, Mr Shorten said his mother had only been able to become a lawyer in her fifties and had found it hard to get work as a barrister.

"I just wish some newspaper outlets would do some of their homework beyond that. She got about nine briefs in her time. It was actually a bit dispiriting," Mr Shorten said.

SMH/The Age