Up to 40,000 people may have been tested with faulty kits made by the Chicago-based Abbott Laboratories Inc and used by the National Health Service over the past six months.
As government health officers stressed that the chances of the faulty test kits producing the wrong result were "very tiny", Aids charities predicted agonising delays and accused ministers of dithering and keeping information from the public.
Although the manufacturers stopped distributing the test on 25 March, the Department of Health decided to postpone action until after Easter, only to see news of the faulty kits leak out in the press.
Derek Bodell, director of the National Aids Trust said it could take months to repeat tests.
"Tuesday morning will be bedlam and the impact will take months to be absorbed - particularly as people are usually asked to take two tests several months apart," he said. Aids workers are also concerned that many people may not be traceable because they gave false names. Between 20,000 and 40,000 of the Abbott tests were carried out in Britain in the six months between 27 September and 25 March. The test produces a false reading when the blood sample contains exceptionally high amounts of HIV-infected blood. About two million kits have been sold worldwide.
Nick Partridge, chief executive of the Terrence Higgins Trust, warned that clinics that used the faulty kit would find six months' work waiting for them on Tuesday. "There are bound to be delays in getting results," he said. "No one yet knows how long they will be." The trust and other Aids charities accused ministers of failing to react quickly enough.
Mr Partridge said that health ministers and senior civil servants had gone on holiday and that the department's communicable diseases unit had seen staff cuts which left it ill equipped to cope with the crisis. "If they had made an announcement on 1 April, we would have had four clear working days," he said.
"Then there are the people who were told they were clear who may be infected. They should have been warned at the earliest opportunity not to have unprotected sex."
The Government's deputy chief medical officer, Graham Winyard, said he "deeply regrets" the way details of unreliable HIV tests emerged through the media. "We were planning to make the situation public next week when more detailed arrangements, including the arrangements which local clinics will need to have, could all have been put into place," he said.
"It is very unfortunate that this has come out now, and undoubtedly a lot of unnecessary distress will have been caused."Reuse content