Have the cracks begun to show in Sky's duty of impartiality?

Ian Burrell explores the background to Adam Boulton's outburst

For 21 years, Sky News has been regarded by left-leaning politicians as the most acceptable face in Rupert Murdoch's hydra-headed British media business. Committed to the rules of impartiality which govern British news broadcasters, the network has been held up as a shining example that contradicts the theory that every outpost of the Murdoch empire is signed up to the Australian-born tycoon's personal agenda.

Sky News has repeatedly thrashed its bigger BBC rival in television awards ceremonies and has, for almost a generation, been the channel of choice for the newsrooms of national newspapers who admire its speed and agility in covering breaking stories.

But the cracks are starting to show at Britain's original rolling news channel. The gripping news video on which it made its name is now as likely to be viewed on YouTube or Facebook and feature the hissy fitting of Sky's best-known presenters, rather than moments of historical importance. Political editor, Adam Boulton, and news presenter, Kay Burley, have become stars of the internet and favourite targets for Sky's critics. Both have recently faced calls for their sacking and been the subject of mass complaints to the media industry watchdog Ofcom.

Monday afternoon's onscreen meltdown by Boulton, who engaged in a live-on-air slanging match with Labour adviser Alastair Campbell, has become an online hit. Yesterday Mr Campbell stoked the fires on Twitter by comparing the episode to the moment in 2001 when John Prescott punched a voter.

"When JP punched someone, pompous Boulton said he must go! Wonder if same rules for TV hacks losing it live. Thought the headbutt imminent." He later claimed that Boulton's whine was noisier than the famous roving Skycopter.

The network responded that its political editor had "defended his integrity, and by implication Sky News's, against an attack by Alastair Campbell". It released a transcript of the exchange, in which Mr Campbell relentlessly prodded the journalist over his supposed sympathy for the Conservatives, rather like a zookeeper trying to get a caged animal to bare its teeth. "You're obviously upset that David Cameron is not Prime Minister." "I'm not upset, you are, you keep casting aspersions..."

Boulton may have been defending his integrity but his loss of cool will not have helped the credibility of one of Britain's most respected political journalists. Before the night was out he had erupted again, in a furious challenge to Culture Secretary, Ben Bradshaw, who appeared amused and mocked Boulton with the comment: "I know you feel very sore about this." Mr Bradshaw later posted on Twitter that, after coming off air, the Sky political editor had warned him: "Don't you dare talk to me like that!"

Boulton's impartiality had been questioned when more than 100 viewers complained to Ofcom over an interjection by the journalist during the second televised debate, which he was moderating. Boulton's reference to a newspaper story criticising Nick Clegg drew a curt response from the Liberal Democrat leader and led to online campaigns over "Sky News Bias Against Nick Clegg".

The Campbell ruckus was the continuation of an altercation on election night when, shortly after 2.30am, Boulton reacted angrily to a perceived insinuation of bias. "This is a serious allegation and if you are going to make it you have to substantiate it," said the Sky man. "Adam, I know you take yourself terribly seriously..." began the antagonistic spin doctor, apparently knowing the buttons to press. "Get off your high horse for two seconds," Mr Campbell went on. "Anyway Adam calm down, enjoy the evening. Maybe we can have a more sustained dialogue in the future." When the dialogue resumed on Monday the personal animosity rose to an excruciating crescendo.

Though this has been highly entertaining, it has come at a delicate time for BSkyB, which is locked in a legal battle with Ofcom over the regulator's decision to order the satellite broadcaster to drastically cut the price that it charges rivals such as Virgin Media and BT for carrying Sky's valuable sports coverage.

Tensions are running high, on and off the air. James Murdoch, chair of News Corp's Europe and Asia operations and non-executive chairman of BSkyB, recently stormed into the offices of The Independent to make an angry complaint over an election marketing campaign that accused his family's news organisations of having political affiliations. Other parts of Rupert Murdoch's media business, including his national newspapers, have campaigned heavily for the Conservatives and there have been persistent rumours, firmly denied by the Tories, that a deal has been struck over future media regulation.

In January, John Ryley, head of Sky News, told an audience at the Cambridge Union that the impartiality rules governing British news broadcasting should be scrapped. Though Sky argues that it is not in its commercial interest to provide its customers with anything other than a politically impartial service, Murdoch Snr is known to be frustrated that he cannot establish a British version of his American television network Fox News, which is populist and unashamedly Republican.

In recent months, the confrontational interviewing style of Fox presenters such as Bill O'Reilly has been mirrored by Burley. Last weekend the presenter aggressively confronted David Babbs, a spokesman for the 38 Degrees electoral reform group, which was demonstrating in Westminster. "What are you protesting for?" she said. "Why don't you just go home!"

The interview led to "Sack Kay Burley" becoming a top trending topic on Twitter. Later, a live interview conducted by Burley from Westminster was hijacked by a protester who screamed "Sack Kay Burley" and "Rupert Murdoch is poison".

Burley, who faced 880 (unsustained) complaints to Ofcom over an interview in which the singer Peter Andre started crying, shrugged off the abuse as "democracy in action". Boulton, writing in the New Statesman this week, complained of being accused of being a "Murdoch lackey" by "the Trotskyist faction of the Fair Votes Now march" and said he was "appalled" by the suggestion by Labour's Ed Balls that Sky News was "deeply partisan".

He said he didn't vote for any party. "And not just because I like to spend most of polling day asleep, charging up for the 26-hour shift that starts for me when the polls close." Sky News may claim not to be in bed with anyone, but its esteemed political editor might be ready for a little lie down.