The head of Channel 4 News says it is impossible for journalists to cover the Iraq war effectively.

Dorothy Byrne told students at the University of Lincoln that broadcasters were not showing the British public what was really happening in Iraq because journalists have to be protected by the military.

She said: "Iraq is now so dangerous it is almost impossible to cover the war properly.

"Journalists who travel about the country go under the protection of the US or British Army and so there are limits to what they see.

"Reports often look like real reports: they are smooth and professional. Yet their information may well have come from their headquarters in London or Washington.

"Television needs to flag this limitation in covering the war. We are not showing the whole truth and it's our job to tell the public precisely that."

But she did tell her student audience that local Iraqi journalists were increasingly being used.

She said: "These Iraqis gain access to different events and sources and so help to provide a different perspective. Thus the dangers limit us – but also provide us with opportunities."

Dorothy did not reserve her criticism for coverage of the war in Iraq. She also attacked TV coverage of the issue of climate change, telling her audience that television executives showed little interest in the subject when she chaired a session at the conference for broadcasters in Amsterdam.

"The trouble with climate change, they said, is that it's not new. TV likes new things: a glacier melts, a hurricane flattens a city. But this is the wrong approach. The subject is too important for us to be limited by too narrow a concept of what is new."

She also claimed that journalists' desire to present a balanced story is impeding their coverage of global warming.

Today, she said, some journalists felt obliged to include the views of those who deny the reality of global warming even though they tend to be representatives of oil interests.

She said: "There is now a consensus in the scientific community that man-made global warming exists - though there is a debate over its extent and what can be done about it."

Dorothy Byrne is a visiting professor at the Lincoln School of Journalism, part of the University of Lincoln.