The veterans will march slowly down Whitehall from Trafalgar Square before handing back their medals one by one on the steps of the headquarters of the Ministry of Defence.
The protest by upwards of 50 veterans, which coincides with the seventh anniversary of the end of the Gulf War, is expected to attract worldwide media interest, with camera crews from Russia and America among those in attendance.
The veterans said yesterday that although the medals were important to them, they needed to make a gesture which would make the public aware of their plight.
Tony Flint, of the National Gulf Veterans and Families Association (NGVFA), said that veterans were now dying at the rate of two a month.
During the war the troops were exposed to a multitude of chemicals in the form of vaccinations, anti-chemical warfare tablets, pesticide sprays and possibly the fallout from a destroyed Iraqi chemical weapons dump.
Among the symptoms they report are cancers, chronic fatigue syndrome, nervous disorders and depression. Many have committed suicide.
Mr Flint said: "We are disgusted and frustrated at the lack of practical help we are given. Handing back the medals is the only way we can think of to highlight our situation. Nothing like this has happened before."
He added: "We were proud to receive the campaign medals but some of the other guys have already had to sell theirs off to make ends meet."
A letter will be presented to the MoD, complaining at the treatment of all British servicemen after they leave the armed forces.
Tomorrow veterans will lay wreaths at the Cenotaph in remembrance of comrades who died during the conflict and 160 wooden crosses will be left in memory of the veterans known by the NGVFA to have died since the war.
The veterans' concerns that they were not being given enough support increased last week with the news that a leading Scottish scientist had been forced to turn to the American billionaire Ross Perot to fund his research into Gulf War illnesses.
Dr Goran Jamal, a consultant at the Institute of Neurological Sciences at Glasgow's Southern General Hospital, has been unable to continue his much-valued work due to lack of government funding. He turned to Mr Perot because he had financed other Gulf War illness research in America.
British-based research into the conditions of the veterans is not expected to be ready for another two years.
The MoD insisted yesterday that the issue was being taken very seriously and that all was being done to try to help those who are ill.
A spokesman said: "The medals will be received with sadness. We realise that if people are going to make this gesture they don't do so lightly.
"We are keen to meet them but feel they are pushing at an open door, because the department feels it is doing as much as it can. It's a shame."Reuse content