Of the 53,500 UK troops deployed to the Gulf war in 1990-91, there are now close to 7,000 who have received a payment or are in receipt of an ongoing war pension for illness or injury relating either to their preparation to deploy or active service.

The Gulf war has been labelled the most toxic war in history. Troops were subjected to a multiple immunisation programme of up to 14 vaccinations prior to deployment, followed by exposures to organophosphates (and other pesticides), nerve agents to counteract the effects of chemical warfare, depleted uranium, environmental hazards, chemical weapons such as sarin and cyclosarin, and smoke from burning oil wells.

Completed research in the UK has now discounted most of these as the single cause of Gulf war illnesses. However, work is currently under way in the US and elsewhere investigating the possible "cocktail effect" of these multiple exposures.

Research has confirmed, however, that Gulf war veterans are more than twice as likely to report symptoms of ill health, and to be suffering more severely from them, than their military contemporaries of equivalent age, gender, rank and branch of service. Symptoms largely fall into four categories: musculoskeletal, neurological, respiratory and psychological.

Sadly, even though 16 years have passed, the veterans and the scientific community are still no clearer on the causes of their illnesses, some of which have proved terminal. Epidemiological studies used to investigate causal links with illness have been hampered by the lack of accurate data, including service records and medical and/or vaccination records. Health surveillance was not carried out during deployment, or immediately post deployment. Additionally, this lack of clarity on exposures has resulted in lengthy delays for veterans seeking pensions and compensation for their conditions.

Still more controversy surrounds administrative problems with the programme of medical countermeasures in the lead-up to and during deployment of British troops to Kuwait and Iraq. In 2003, the government spokesperson for defence admitted in the House of Lords that these included breaches of the policy of voluntary informed consent on immunisations, the use of unlicensed and unproven vaccinations, and ignoring medical advice from the Department of Health on the potential adverse reactions of administering the vaccine cocktail.

Tomorrow, the Royal British Legion will host a conference in Birmingham for veterans of the Gulf war. The conference will aim to update veterans - many of whom are in broken health - on the progress that has been made since the release of the findings of an independent public inquiry into Gulf war illnesses in 2004, and offer input on future policy initiatives, including demands for a one-off payment of £10,000 to those affected.

The day's programme will include a speech from the minister for veterans, Derek Twigg - the first time in 10 years that a veterans minister has spoken to Gulf veterans about their illnesses - as well as a presentation from Dr Harcourt Concannon on how the military's pensions appeal tribunal has effectively forced the Ministry of Defence to accept the umbrella term "Gulf war syndrome" on selected hard-fought cases.

The government has continually stated that the time is not right for a public inquiry into the causes of Gulf war illnesses and the handling of the surrounding issues; a policy which has bred a feeling of rejection among veterans. The reasons given for this have been that scientific and medical investigations are ongoing.

However, many scientific and medical experts have now concluded that further clinical or causal investigations will probably not produce any further useful outcomes. The legion has renewed its call on the government to make a definitive statement regarding a public inquiry at tomorrow's conference.

The government has recognised the call from Gulf veterans for further research into rehabilitation and health and social care models that can improve the quality of life and general health of veterans and their families. Identifying useful models needs to become a greater priority.

In 2004, the Rt Hon Lord Lloyd of Berwick made a recommendation for an ex gratia payment for Gulf war veterans as part of the findings of his independent public inquiry into Gulf war illnesses. Wednesday's conference will seek support for the immediate offer of the ex gratia payment - based on the government's failure to protect veterans, the treatment they have received and the resulting anxiety.

The £10,000 payment is in line with other UK ex gratia payment schemes. It should be awarded to all Gulf war veterans who have received a gratuity or war disablement pension, Gulf war widow(er)s in receipt of a widow's pension, and children of Gulf war veterans who are in receipt of a war orphan's pension.

· Frances Hoy is head of PR and campaigns and Lisa Wise is head of public policy for the Royal British Legion. The group's Gulf War Veterans' Conference will be held at the Radisson SAS Hotel, Birmingham tomorrow