An analysis of the political content in one of media mogul Rupert Murdoch’s major outlets has demonstrated anti-Labor commentary is seven times more likely on the news service than negative rhetoric about the Coalition.

Amid accusations of a “clearly partisan” bias against Opposition leader Bill Shorten at News Corp leading to a vicious slanging match between the two camps, The New Daily decided to check on whether there was a clear difference in the way the Labor Party was spoken about on the Murdoch-owned television station Sky News.

Research conducted by The New Daily confirms perceptions of anti-Labor bias amongst conservative commentators, while the Liberal Party and Pauline Hanson’s One Nation Party were the subject of glowing commentary.

Sky, previously available only on subscription, became much more politically potent last year after it began broadcasting free to air in regional areas through the WIN Network.

Many of Sky’s commentators, including Andrew Bolt, Chris Kenny, Paul Murray, Alan Jones and Peta Credlin, draw the ire of the left.

Most, but not all, are screened in the evening and have attracted the nickname “Sky After Dark”.

Across a three-day period TND found there were more than seven times the number of negative comments directed at Labor than at the Liberals –194 negatives to 27 respectively.

One Nation received almost three times as many positive comments as negative: 26 to 9.

The Greens received not one single positive comment.

The trigger for the current imbroglio, which has put media bias front and centre of the campaign came after a Murdoch paper headline “Mother of Invention” queried Labor leader Bill Shorten’s version of his mother’s struggles and accused him of “slipperiness on detail”.

An emotional Shorten described the attack as “a new low”.

My mum. #auspol #qanda pic.twitter.com/VXi04aLoYS

— Bill Shorten (@billshortenmp) May 7, 2019

Since then, Labor identities have ploughed in – Tanya Plibersek suggesting the company was not paying its fair share of tax and Wayne Swan accusing Murdoch of “misuse of power”.

Even some News Ltd’s journalists joined in, with the award-winning Tony Koch accusing his former employers of “shameless bias”, while their social affairs reporter Rick Morton said “the craziness has been dialled up”.

• More: Mounting evidence tide turning on Murdoch 

Mr Shorten’s announcement of millions in extra funding for the ABC, which is routinely accused of left-wing bias by its right-wing critics, has left him accused of politicising the ABC. Experts say the media polarisation is damaging democracy because the public do not know who to believe.

A Sky News spokesperson told The New Daily: “We passionately debate and discuss the issues on the national agenda through our journalism, commentary and analysis, which is important to a healthy democracy, and are committed to doing so in a way that meets editorial, journalistic and community expectations.”

However TND’s sampling of its commentary shows a high level of hostility towards the Labor Party.

On one day alone, Kenny began by concentrating on the costing of Labor’s climate change agenda: “There will be a lot of concern about the knock-on effects of these Labor policies.”

Later Credlin, Tony Abbott’s former chief of staff, accused Labor of a “woeful inability to handle money”.

Bolt continued the attacks, accusing Mr Shorten of backtracking on wages policy, after which broadcaster Jones then stepped in, describing Shorten as “clueless”.

He was followed by Murray, who suggested the Labor leader was telling “porky pies”.

Associate Professor Timothy Dwyer, of the Sydney University media department, told The New Daily the attacks on Shorten were clearly partisan.

“Australia’s media is dominated by two large commercial organisations, News Corp and Nine Entertainment,” he said.

“Their interests are aligned with the pro-big business stance of the Coalition. They have enormous power to set a partisan agenda.”

Professor David McKnight, author of Rupert Murdoch: An Investigation of Political Power told The New Daily no one should be surprised that News Corp was displaying political bias.

“A lot of people assume News is a normal commercial news organisation, and it is not. Rupert Murdoch enjoys, and is determined to exercise, political influence,” he said.

“In News you have a very politically motivated news outlet –online, print, free to air and subscription. All of this is building a very strong right-wing media. It is an appalling vision of the future.”

Senior researcher in journalism at the University of Melbourne, Dr Denis Muller, told The New Daily the impact of Sky After Dark went well beyond its limited audience.

“The New Daily’s research conclusively demonstrates that just like News Corp newspapers, Sky is heavily biased against Labor. It is obvious on the numbers,” Dr Muller said.

“Sky at night debases political discourse. It lowers standards generally. It has a licensing effect, and that is where it does its most damage – it allows for vile and vulgar material in the mainstream.”