Many people with ME are unable to continue working
Chronic fatigue syndrome costs the British economy billions of pounds each year, a report suggests.
Research carried out for the charity Action for ME suggests the total cost runs to £3.5bn annually.
This represents almost £15,000 for each person with the syndrome, also known as ME (myalgic encephalomyelitis).
The figure is based on the cost of medical treatment, loss of earnings and the cost of state benefits.
According to Action for ME, an estimated 240,000 Britons have chronic fatigue syndrome.
The Department of Health acknowledged ME is a medical illness only last year. It followed years of campaigning by patient groups.
Health Minister Jacqui Smith announced on Monday that £8.5m would be made available for services specifically designed for people with ME.
This will include establishing centres of expertise across the country and satellite multidisciplinary community teams to develop services within primary care to support GP's and other health professionals.
Money will also be made available for reseach, and for education and traning for health professions.
But campaigners say that much more money is needed to tackle the problem.
The new report, by researchers at Sheffield Hallam University, suggests the government loses in the region of £2.2bn each year because of the condition.
This represents the loss of tax revenue from people who have to stop working because of the condition and the cost of paying incapacity and other benefits.
By developing a better understanding of this illness and finding more effective treatments that will put an end to the needless waste of lives and money
Action for ME
The cost of treating patients with ME is estimated at £210m per year or £900 per person.
Most of this money represents the costs of medical consultations and tests to exclude other illnesses and money spent on drugs aimed at managing the condition.
The charity said the findings highlighted the need to carry out urgent research into the condition. The cause of ME is unknown and there is as yet no effective treatment.
It has called on the government to make £35m available to fund research projects, which it says represents 1% of the estimated cost to the economy.
Chris Clarke, chief executive of Action for ME, said: "£3.5bn is a huge amount of money and if the government invested even 1% of that cost into research it would undoubtedly be money well spent.
"It is only by developing a better understanding of this illness and finding more effective treatments that will put an end to the needless waste of lives and money."
The Medical Research Council said it had stepped up efforts to encourage researchers to carry out studies into ME.
It said research into the condition is now regarded as a priority.
It published a research strategy at the beginning of May, which sets out potential ME research areas.
Scientists who submit proposals under this scheme have a greater chance of receiving MRC funding than others.
In a statement, the council said: "Proposals received under this initiative will benefit from additional 'weighting' when being assessed in competition for MRC funds as ME has been designated a current priority are for research."