At issue is The Guardian's investigation into The Connection, an award- winning Carlton documentary about the drugs trade which the newspaper claimed was a fake.
A Hard News special on Channel 4 this evening corroborates the newspaper's central allegations against The Connection, but questions the prominence The Guardian gave to the investigation, and the way in which it was conducted.
Hard News accuses The Guardian of adopting a "high moral tone ... as it set itself up as a watchdog of television". But, the programme continues, the paper "did not always live up to its own professed high standards".
Chief among The Guardian's alleged sins appears to have been an aggressive interviewing technique deployed by the reporters Michael Sean Gillard and Laurie Flynn on The Connection's producer, Marc de Beaufort.
David Lloyd, head of news and current affairs at Channel 4, said: "I set a lot of store by the restraint you show in investigations. In my personal opinion, it would have been better if more restraint had been shown in the coverage."
The attack has dismayed The Guardian, which sponsors the channel's film production arm, Film on Four.
"We cannnot see why Channel 4 has cleared an hour of its schedule to be so critical of newspaper articles whose central allegations proved to be true," said a Guardian spokeswoman. "By all accounts, this is a sloppy programme. We are severely troubled by the way it came to be commissioned.
"However, unease about one programme in the schedule will not affect our editorial or business relationship with Channel 4."
Apart from the commercial tie-up, the bonds between the newspaper and the network are close. Michael Jackson, the channel's chief executive, and Georgina Henry, The Guardian's deputy editor, are longstanding friends, while David Brook, Stevan Keane and Polly Cochrane have all left the newspaper recently to join Channel 4 as director of strategy, commissioning editor of night-time programmes and head of marketing respectively.
According to one Channel 4 source, Mr Jackson and Alan Rusbridger, editor of The Guardian, exchanged "very aggressive and caustic correspondence" in the weeks leading up to tonight's broadcast.
Another Channel 4 source said: "This has created a lot of tension. Despite setting themselves up as a high moral judge, The Guardian doesn't seem to think anyone has any right to look at its methods. There has been lots of concern from them about the tone and the content of the programme."
Sources at the company responsible for Hard News, Clark Productions, believe that Guardian reporters were responsible for leaking black propaganda about this evening's special. A report in Private Eye claimed that two producers had walked out on the production because they felt it had no evidence of wrongdoing on The Guardian's part. In fact the two producers left because they had other work commitments and Hard News was taking longer than expected.Reuse content