Ministers say they have met a flagship target of 100,000 coronavirus tests a day – but face accusations that the figures have been massaged.
Official numbers include tests yet to be carried out, sources confirmed.
Tests posted to people’s homes but not yet returned have been counted, they said.
Health secretary Matt Hancock on Friday announced the government had exceeded his 100,000 target, saying the number of tests on the final day of April was 122,347.
A leap in tests announced on Thursday, to 81,000, fuelled speculation that ministers had succeeded in what was described as a Herculean task.
But the figures have been boosted by home testing kits being sent to individuals through the online retailer Amazon.
Sources confirmed the tests were counted when they were sent out, not when they were returned.
On 30 April, more than 27,000 home tests were sent out.
Professor John Newton, from Public Health England, said a further 13,000 tests were delivered through the government's satellite process, where they are sent to centres such as hospitals and NHS sites.
Individuals cannot receive a diagnosis in their own home. Instead they must use the test kit and send it to be processed in a laboratory.
Government sources insisted ministers should not be held responsible for delays over which they had no control.
They also said the method of counting had not changed since the home tests were rolled out at the start of this week.
The government has always said the target applies to tests carried out, not to capacity.
But on Tuesday, in a little-noticed development, the Department of Health tweeted that its statistics on the number of tests included “tests posted to an individual at home” as well as “tests conducted”.
A government source said: “For home tests kits, when we can’t control when people will do them ... from when we have posted the kits out to people, when we have done as much as we can, that’s when we have counted the tests from. And that’s what it has been from the start.”
Shadow health minister Justin Madders said: “We want the government’s test, isolate and trace strategy to succeed, and welcomed expanding who was eligible to get a test, but counting a test put in the post is not the same as a conducted test and getting results.
“Ministers should focus on making sure these tests are administered effectively rather than moving the goalposts to hit their own arbitrary target.”
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