Dr Hilary Jones warned Good Morning Britain viewers to "be wary" of "inaccurate" antibody tests being sold amid the global coronavirus pandemic.
Hilary joined GMB hosts Susanna Reid and Piers Morgan on the show on Wednesday, and issued a warning about the reliability of new tests being sold by companies.
Telling viewers to be "wary" he hit out at said companies, and said the selling of the tests were "illegal".
Hilary explained that it was not yet possible to confirm if such a test would provide a reliable result, and until they could they should not be sold.
Susanna had asked him about this test and the antigen test used to see whether someone has COVID-19 or not.
Asking about the reliability, she asked the doctor for his professional view with tests continuing to be sold.
It's then that he detailed both tests, before issuing a warning to anyone thinking of buying an antibody test.
He commented: "The most important test is the antigen test. This is the test that shows whether someone has actively got the infection which means we can isolate them, and keep them away from other people to prevent transmission.
"Later down the line it will be useful to know who is immune and who can go back to work and be around patients, and who doesn't have to worry anymore about the virus."
Speaking of the antibody tests, he went on: "It's really difficult to get an antibody test that is accurate enough to be reliable and usable.
"All around the world we're having the same problem, there is no test at the moment which can give you enough sensitivity and specificity, in other words reliability, to rule out false negatives and false positives.
"Until we get that the antibody test isn't very worth using."
He went on: "Let me just say this, there are plenty of companies out there trying to peddle tests, which aren't reliable, to members of the public which by the way is illegal.
"People need to be very wary of not buying antibody tests because they're just not reliable at the moment."
Good Morning Britain airs weekdays at 6am on ITV.