LONDON (Reuters) - Britons should not purchase unapproved antibody tests to find out if they have had the coronavirus, the official in charge of the government’s testing program said on Saturday, warning that they could not be relied upon and may put people at risk.

Britain, like many other nations affected by the coronavirus epidemic, is trying to find a way to test whether citizens have had the virus and are now immune. But, scientists are yet to find a reliable method that can be produced on a mass scale.

John Newton, National Coordinator of the UK Coronavirus testing program, warned against purchasing unapproved tests online for personal use, or in bulk for firms to test employees.

“Please don’t buy or take any unproven tests,” Newton said in a statement issued by the health department. “They may not be reliable for your intended use; they may give a false reading and put you, your family or others at risk.”

Knowing whether a person has immunity from the virus is seen as a crucial step toward returning to normality after a pandemic in which more than 147,000 people have died and much of the world economy has been shuttered or severely disrupted.

Britain previously said it had purchased 3.5 million so-called antibody tests with the hope of quickly rolling them out to the public. However, those tests have proven insufficiently reliable and the government is now supporting domestic research into a creating viable test.

Such tests work best around one month after a person has had the virus and may be possible to take at home using a finger prick that delivers a result within 20 minutes, Newton said.

“Such a test could, if developed in such a way that they could be reliably used at home and be sufficiently accurate, be a game-changer,” he added.