Only one in 500 of the asylum seekers screened for tuberculosis (TB) in Kent last year tested positive for the disease, SocietyGuardian.co.uk has learned.

Of the 4,219 asylum seekers screened for TB at the Dover induction centre between April 2004 and January 2005, only nine - or 0.2% - tested positive for the active, contagious, form of TB.

The figures were released after the Conservative party announced proposals to screen for TB all non-EU migrants applying to live or work in the UK for more than six months.

Although the proposals do not cover asylum seekers, the Liberal Democrats and centre-left thinktank the Institute for Public Policy Research warned that they overplayed the link between asylum and immigration and disease.

Britain is the only EU country to see an increase in TB cases over the past 10 years, with figures showing that the number of infections in England and Wales rose by 20%, from 5,798 in 1992 to 6,891 in 2002. Two-thirds of people with TB in the UK were born abroad, although it is possible that they contracted the disease after coming to Britain.

However, the evidence from the Kent scheme - which carries out TB screening in Dover, Margate and Ashford - would suggest that asylum seekers are not bringing the infection to the UK.

The project, set up in 2001 with funding from the Department of Health, the Home Office and local primary care trusts (PCTs), screens all newly-arrived asylum seekers for TB and other infectious diseases, providing them with an initial health assessment.

“Detecting each of these cases is worthwhile, both for the health of the individual concerned and on public health grounds,” a spokeswoman for the Shepway PCT, in Kent, said. “The earlier that TB is detected the better the outcome and the less risk to other people.”

The scheme was the first health screening service for asylum seekers in the UK. In its first year of operation none of the 5,500 asylum seekers tested were found to have the active form of TB. Further screening projects have been set up in Leeds, Barnsley and Greater Manchester.

Around one third of the world’s population - some two billion people - carry the TB bacterium, but most never develop the active disease. Screening only picks up the 5% of people with the active form of the disease. Another 5% carry the dormant form of the bacterium, but do not develop symptoms for years.