The judges said the armed forces must normally abide by European Union rules on equal treatment between men and women.

But the Royal Marines was entitled to exclude females because it involved "special combat units pursuing activities for which sex is a determining factor".

The case was brought by Angela Sirdar, from Norwich, Norfolk, who was turned down for a cook's job with the marines.

Mrs Sirdar said her rejection because she was a woman was a breach of EU equality laws.

Judges upheld earlier decision

But judges agreed with the Ministry of Defence that in the Royal Marines even cooks must be able to carry out special duties.

The verdict said: "The fundamental characteristics of the Royal Marines is their rapid deployment capacity as assault troops in a wide variety of military actions and close engagement with the enemy."

'Women would hamper operations'

The judges said the marines worked on the "interoperability" principle in which each individual must be able to perform a series of tasks and fight as part of an infantry unit, independent of his specialisation.

They endorsed the ministry's insistence that the employment of women would hamper the maintenance of "interoperability".

The key to the ruling was a clause in the EU equal treatment law allowing some strictly defined exceptions to the equality principle, particularly where gender is a "determining condition for the exercise of the activity in question in view of its nature".

Marines can remain 'Exclusively for men'

Each EU member state had a margin of discretion in such cases, said the judgment, adding: "The Court considered that in the circumstances of this case the national authorities could, in the exercise of that discretion, reserve access to the Royal Marines exclusively for men owing to the specific conditions governing their deployment as front-line commando units."

Commenting on the decision, the chairman of the Equal Opportunities Commission, Julie Mellor, said: "Britain needs the best army possible. It can only be damaging for Britain to be limiting recruitment to many of these posts to half the population."

Mrs Sirdar had been a British Army Cook for 11 years and had requested a transfer to the marines after being made redundant from the Royal Artillery in 1994.

But she was told the marines did not employ females.

Her sex discrimination claim at an employment tribunal in Bury St Edmunds, Suffolk was passed to Luxembourg to decide the scope of EU equality laws on "access and employment in the army or in one of its bodies".

Final verdict

Earlier this year the European Court's Advocate-General delivered an advisory "opinion" questioning the government's claim that a female British Army cook could not work in the elite unit because "military effectiveness" might be compromised.

He called for a rigorous check into whether the "special conditions" under which the marines operate made the total exclusion of women really necessary to meet defence requirements.

There were no such caveats in Tuesday's final verdict, which comes five years after Britain amended national law to end sex discrimination in the armed forces to bring the country in line with the EU equal treatment rules.

The 5,900-strong Royal Marines represent just 2% of the British armed forces.