In anticipation of a war against Iraq early next year, troops are being given at least 10 vaccines, including one for anthrax, and pills to ward off the effects of a chemical attack.

Yet scientists have still not agreed on how this pharmaceutical cocktail - as well as the use of pesticides and the effect of depleted uranium from anti-tank shells - will affect the health of the troops. The spectre of a repeat outbreak of what is known as Gulf war syndrome is a real one, say veterans' campaigners.

Dr Lewis Moonie, the veterans' minister, dismisses these fears. Two weeks ago he told Labour MP Llew Smith he was confident there would be "no significant adverse health effects" associated with the use of the prophylactics.

An investigation by the Guardian has also discovered that the agency responsible for the welfare of British troops sent into battle, the defence medical services (DMS), is woefully understaffed, relies on reservists that will have to be withdrawn from the NHS and has in the past had to rely on coalition partners who may not be present in this new conflict.

At a conference on the DMS two weeks ago Bruce George, the chair of the Commons defence committee, said the services had been in "indisputed crisis for some years" with an ability to provide only four of 14 field hospitals needed for a large-scale war effort. The latest figures with a staff shortfall of 23% "do not make happy reading," he said. For consultants the position was "horrendous" with a 50% shortage. Gulf war veterans on both sides of the Atlantic have complained of a lack of funding and commitment from governments after the first signs of the illnesses occurred in mid-1993. The veterans are supported by former major general Robin Short, the director general of army medical services in the Gulf war. In a parallel investigation by Channel 4 News to be shown tonight, he says: "The evidence I have is when they come back the care ceases. I don't think the resources have been provided to allow the medical services to do their job.

"There has been a reliance on discharging the soldiers and the NHS to pick up the bill for those who require further treatment. The one thing I will remember from the Gulf conflict is the fact that we lost the confidence of the soldiers."

Only in the last six years, mainly with American money, have extensive experiments begun into the illnesses. The main British one, under way at Porton Down since 1997, will not be finished for a year.

Labour made a "debt of honour" promise to the veterans when they came to power in 1997. But the MoD, which denies that Gulf war syndrome exists, has long been accused of dragging its feet.

One leading American researcher, Robert Haley, recently accused veterans' minister Dr Moonie of "a lack of awareness of certain facts on which there is widespread agreement in the US".

In an interview with Channel 4, Professor Alistair Hay, a chemical and biological expert at Leeds University says: "The Americans have pumped into this a huge amount of money to try and assess whether Gulf illness is a problem and what caused it. I have to say our response in the UK has been particularly poor in comparison. What was put in was put in reluctantly and very late in the day."

Earlier this year the US veterans affairs department accepted that Gulf war illnesses are likely to be neurological after Dr Haley concluded they were probably caused by brain damage from low level exposure to nerve gas when an Iraq military dump was blown up, and other organophosphate exposures in vaccines and pesticides used by the troops. Lord (Alf) Morris, another veteran campaigner, says: "The veterans are saying the US is acting while the UK is studying."

The US department also agreed this summer to compensate veteran victims for the rare neurological motor neurone disease which has manifested itself at twice the rate in veterans as in rest of the population.

In a series of letters and parliamentary answers recently, UK defence ministers have claimed that the armed forces are significantly more informed about medical counter-measures than before and that new detection equipment and record keeping, both subjects of criticism in the last Gulf war, have been introduced. But in a letter to Lord Morris in October, the defence minister Lord Bach conceded: "Obviously we cannot guarantee that deployed forces will not suffer ill-health but we are doing everything we can to minimise the risks."