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..."