In a move that is expected to be followed by other government departments, it has hired media consultants to assess every article in the national and regional press according to whether it is positive, negative or neutral.

It identified 21 correspondents who reached the most readers, either because they wrote a lot or because their papers had the biggest circulations. According to the consultants Millward Brown, nine of them had nothing positive to say about the NHS.

They identified Nic Cecil of the Sun as "the journalist with the highest reach". Two of his articles on the NHS during the measurement period in December were rated negative, one positive and one neutral.

The Daily Mail was the paper with the "highest reach". The overwhelming majority of its 59 articles on the NHS during the month were negative or neutral, with only about 7% carrying a positive message about the NHS.

The exercise was part of a ?200,000 programme of research into public attitudes to the NHS.

It found that 87% of people who recently visited the GP were satisfied with the service. High satisfaction ratings were also recorded among people with recent experience of inpatient treatment (92%) and an outpatient visit (85%).

But in a poll of the general public, only 62% said they were satisfied with the running of the NHS overall.

Ministers are understood to believe that negative press coverage is one of the main reasons why people without recent experience of the NHS are more negative about it.

Although its press officers already had a good idea of which papers gave negative coverage, the Department of Health said, "it was important to have this established on a scientific basis rather than hunch".

Consultants were able to "inject scientific rigour by carrying out this exercise at one remove from department officials".

The department planned to publish regular reviews of journalists' output over periods of six months. None would be penalised for taking a negative approach, the department said. It added that it was the first department to make such data public.

The extent of each paper's influence was measured in points known as "wots", or "weighted opportunities to see" - based on the paper's circulation and the visibility of the article, including its size, position in the paper and presentation, with or without illustration.

The Guardian had the fifth highest score, behind the Mail, Sun, Mirror and Telegraph. It beat papers with larger circulations, due to its more extensive coverage of the NHS, carrying 87 articles during the month.