The Ministry of Defence is mounting a High Court challenge to a ruling that it must recognise Gulf War syndrome.

A pensions tribunal found that the mystery illness was attributable to service in the 1991 conflict.

Ministers were therefore liable to provide additional compensation for sufferers, the landmark decision said.

But the MoD will dispute the finding, claiming that despite extensive research commissioned by successive defence secretaries since 1994, no evidence exists to prove the link the illness and Gulf service.

The outcome will be watched closely by thousands of ex-servicemen and women who are ready to sue for damages if the ruling is upheld.

Defence officials only recognise what they term "symptoms and signs of ill-defined conditions" (SSIDC).

They recognised that this was the case with former Parachute Regiment officer Shaun Rusling, whom they agreed to pay a 90 per cent disablement war pension.

Rusling's Leeds tribunal was wrongly concerning itself with the "label" of Gulf War syndrome, the government said.

However in May last year tribunal chairman Dr Harcourt Concannon ruled that SSIDC as a diagnostic condition did not cover all the ground embraced by the claim for Gulf War syndrome.

Concannon refused the MoD leave to appeal, saying he was not satisfied "that a reasonably arguable case" had been made by the MoD, forcing the government to take its case to the High Court.

Ministers worry that millions of pounds will have to be paid out to sufferers of the controversial condition if the Leeds ruling is upheld.

Rusling believes there is a "concerted policy" on the part of the ministry's War Pensions Agency not to use the term "Gulf War syndrome" for fear that it will legitimise the disease.

Paul Tyler, a Liberal Democrat MP and member of the Royal British Legion Gulf War Group, slammed the MoD's stance as "scandalous" at a time when many troops face deployment back to the Gulf.

"At a time when British troops are being prepared for a new war against Iraq, it is not only insensitive, but frankly scandalous that the MoD refuses to recognise the illnesses of Gulf War veterans," he said.

"The terrible mistakes of 1991 must not be repeated. In 2003, the MoD is ducking the issue by making vaccinations for soldiers 'voluntary'. With today's legal challenge, one cannot help but conclude that the government is trying to pass their responsibility on to the shoulders of young service personnel."