SCOTLAND'S national clinical director has admitted the coronavirus tests are "a bit rubbish".

Jason Leitch has suggested that the “antigen” tests - are not fully reliable as they can give positive results to people who are not infectious.

It comes as a leading statistician said that thousands of people could be unnecessarily told to isolate under the Government’s ambitious mass coronavirus testing proposals, as a Cabinet minister admitted the technology for the plan does not yet exist.

Professor Sir David Spiegelhalter said the “huge danger” with Boris Johnson’s Operation Moonshot project – which would see millions of UK-wide tests carried out daily – was that there would be a “very large number of false positives”.

Speaking in a web Q&A for members of the business body FSB Scotland, Mr Leitch was asked about the different kinds of coronavirus tests available, and if businesses might be able to rapidly test workers to check if they have Covid-19.

He replied: “Yes, I think that will come. The science is not ready for that yet. I think a number of things will happen.

“Remember, the first, the most important test we're doing just now is the antigen test - looking for virus.

READ MORE: Coronavirus : Scotland actually tests only one-third of capacity, new figures show

"Now the test just now is a bit rubbish. It is positive if it finds live virus, or remnants of dead virus, it can't tell the difference. "So you could still be shedding virus six weeks after you have had the infection, and still get a positive test, and you're not infectious.

“So the test we have just now is a bit rubbish, and the science is trying to improve that test all the time.”

He added: “That's why you hear us talk about testing a lot. It's very important, but it's not the only important thing.”

Professor Carl Heneghan, director of Oxford University’s Centre For Evidence-Based Medicine, described it as "an astonishing admission"

It comes as Boris Johnson said he hopes millions of Covid-19 tests - including some giving results within minutes - could be processed daily.

But experts say there are issues with laboratory capacity for current tests, while the technology for more rapid tests "does not, as yet, exist".

The British Medical Journal says leaked memos show the plan could cost £100bn.

Speaking after his announcement that gatherings in England are to be restricted to six people from Monday, Mr Johnson said the government was "working hard" to increase testing capacity to 500,000 tests a day by the end of October.

And he said that "in the near future" he wanted to start using testing "to identify people who are negative - who don't have coronavirus and who are not infectious - so we can allow them to behave in a more normal way, in the knowledge they cannot infect anyone else".

Prof Spiegelhalter told BBC Radio 4’s Today programme that statisticians were “banging their heads on the wall” at the proposal.

“Mass screening always seems like a good idea in any disease – ‘Oh yes, let’s test everybody’. But the huge danger is false positives – no tests are perfect, it is not a simple yes/no thing.”

He said the threshold would have to be set to a level that would “pick up anything that hints at being infectious”, meaning that the tests would “always generate a very large number of false positives”.

“That doesn’t matter so much perhaps if you’re just being stopped going into a theatre – the point is it is not just a matter of testing.

“You’ve got this whole downstream business that that person will be told to isolate, their contacts will be told to isolate, and so on.

“And if you only have 1% false positives among all the people who are not infectious, and you’re testing the whole country, that’s 600,000 people unnecessarily labelled as positives.”