The UK’s chief medical officer has dismissed suggestions a coronavirus antibody test will be ready to buy online next week.
Professor Chris Whitty said the accuracy of the tests needed to be properly tested before they were made available for public use.
The tests - if proven to work - would show if a person has had the disease, as antibodies are produced by the body to fight off a virus.
It comes after professor Sharon Peacock, director of the National Infection Service at Public Health England (PHE), said it could be a matter of days before coronavirus antibody testing kits would be on the market.
Professor Peacock told MPs that 3.5 million finger prick blood tests had been bought and would be available in the "near future".
It would mark a significant increase in the amount of testing currently being undertaken in the UK.
The Government has said it would ramp up by testing 25,000 people a day, although the current figure is between 5,000 and 6,000.
Prof Peacock said the tests would allow key workers – like doctors and nurses – to go back to work if they have developed antibodies.
She added that a small number of tests would be assessed in a laboratory before being distributed.
People would prick a finger for a small blood sample which would then be analysed by the device to show whether they have antibodies to the virus.
Prof Peacock added: “Once we are assured that they do work, they will be rolled out into the community.
“Testing the test is a small matter, and I anticipate that it will be done by the end of this week.
“In the near future people will be able to order a test that they can test themselves, or go to Boots, or somewhere similar to have their finger prick test done.”
Asked whether this meant it would be available in a number of days, rather than weeks or months, she said “absolutely”.
But speaking at the daily Downing Street press conference, Prof Whitty said members of the public would not be buying these tests via the internet next week.
He stressed that frontline NHS workers would need the tests first so they could get back to work if they have already had the virus.
Prof Whitty said: “I do not think – I want to be clear – that this is something we will suddenly be ordering on the internet next week.
“We need to go through the evaluation, then the first critical uses, and then stretch it out from that point of view.
“We need to do that in a systematic way.”
He added: “The one thing that is worse than no test, is a bad test.”
Prof Whitty said experts would also be collecting information from results of the tests, and needed to make sure “the right people get the test first in order to allow workers to go back”.
Coronavirus: Everything you need to know