Mr Campbell said reporters had given too much credence to what he called "Milosevic's lie machine".

He also accused them of lacking the "daredevil sprit" required to try and force their way into Kosovo and find out what was really happening on the ground during Nato's 79-day air war against Serbia.

BBC World Affairs Editor John Simpson rejects the charges

The prime minister's press secretary was speaking of his experiences after being drafted in to help Nato's spokesman Jamie Shea in Brussels co-ordinate the alliance's media presentation during the war.

His comments came in a rare public briefing at the Royal United Services Institute.

BBC journalist John Simpson accused Mr Campbell putting up "a smokescreen for the failures of spin doctoring".

He said Nato's bombing campaign had not been as successful as the Allies said it was and "the suggestion that this should have been swept aside is not a very impressive one".

Mr Simpson told BBC Radio 4's PM programme: "You can't help thinking that really this is about the failures of spin doctors rather than the failures of journalism."

Journalists 'missed the story'

BBC World Affairs Correspondent Nick Childs: "The media has become a focus for debate"

After turning off his pager Mr Campbell said journalists had often missed the real story during the war. This had not been Nato blunders - such as accidentally hitting civilian targets, convoys, and the Chinese Embassy - but had rather been "war crimes and atrocities" committed by President Slobodan Milosevic's forces against civilians.

One of the most demanding aspects in fighting the media war, Mr Campbell said, had been attempting to cater for the demands of 24-hour rolling television news with its constant need for fresh images and stories.

The Chinese embassy after Nato strikes

He said broadcasters had often falling into a habit of thinking if there were "no pictures" then there was "no news".

Nato had been at a particular disadvantage he said as the alliance had been unable to gather any television images of what was happening inside Kosovo - this had handed the initiative to the Serbs, he said.

By supplying western journalists with images they had been able to get reports of the few Nato mistakes to dominate news bulletins.

"Fighting that Serb lie machine was one of the most difficult tasks we faced and we weren't helped by the fact that the media in our countries didn't think it remotely newsworthy that Tanjug, Milosevic's news agency, claimed we dropped napalm bombs on children or that we bombed old folks' homes," he said.

'Unhealthy relationship'

Mr Campbell also repeated remarks made by some during the campaign that the "health warnings" detailing Serbian reporting restrictions on news items coming from Belgrade at times had been so weak as to be meaningless.

BBC Political Correspondent Laura Trevalyan: "Mr Campbell's frustration was coming through"

He said one American journalist had told him that there was an "unhealthy relationship" between some western journalists and Serb spokesmen.

"I understand the pressures on journalists who fear being kicked out but I believe they should be more open and honest about those pressures."

Mr Campbell then provoked an angry response from some journalists when he said: "The day of the daredevil reporter who refuses to see obstacles to getting the truth, and seeing it with his or her own eyes, seems to have died.

"But surely the starvation of pictures and the denial of access by the Serbs, increased rather than lessened the responsibility of the media to try to find out what was happening there."

Lt-Gen Roddy Cordy-Simpson: Unsure whether to believe Nato

Mr Campbell also took journalists to task for responding with scepticism to information supplied to by Nato sources.

But earlier in the day Lieutenant-General Sir Roddy Cordy-Simpson, who worked in Nato Operations, Bosnia, during 1996-97, said he was unsure whether those speaking for Nato could be trusted.

"There is a considerable discrepancy between what the Nato spokesmen were claiming and the reality on the ground of the damage being done to Milosevic's war machine," he said.