Geoff Hoon's claim that allowing women to serve on the front line could undermine unit cohesion and combat effectiveness has come under fire from researchers.

A study of the army's equal opportunities policies found that while progress was being made, the "historically masculine" culture was still causing difficulties.

Research by the Universities of Newcastle upon Tyne and Sunderland, funded by the ESRC and the Ministry of Defence, found that many male soldiers and officers still find it hard to adjust to the presence of women in the organisation.

And the defence secretary's claim that "military judgement" supported the view that women's exclusion from some combat positions was justified was criticised for his failure to detail the reasons behind it or to cite any scientific evidence.

He was "implying that the very presence of women constituted the risk" said the researchers.

Among the policy documents examined by the study was the official study into Combat Effectiveness and Gender.

That report led to the defence secretary announcing in May 2002 that women would continue to be excluded from some direct combat positions.

But the researchers argued that although the report appeared to support the idea of women soldiers through references to equal opportunities and other policies, closer scrutiny revealed an attitude which viewed women as a disruption.

The media also faced criticism for their stereotypical portrayal of "the sexy or tomboyish woman soldier".

"Women are either portrayed as sexualised, such as Lance Corporal Roberta Winterton, the first serving soldier to pose topless on page three of a tabloid newspaper, or as 'gutsy' tomboy figures who will never be quite good enough to be real soldiers," said researchers Dr Rachel Woodward and Dr Patricia Winter.

"The army is trying very hard to attract and integrate women into the organisation. Equal opportunities policies and attempts to implement these throughout the rank and file should be recognised as an example of best practice," said Dr Woodward.

"Nevertheless, our research revealed attitudes and language used when discussing and writing about women which undermined the army's efforts to portray itself as a progressive employer.

"We found that the army is still a traditionally masculine organisation which is only adapting gradually to the inclusion of women - and this adaptation process is uneven through the ranks. There is evidently great opposition from many soldiers who think the army should be an exclusively male preserve."