British Prime Minister Boris Johnson has sought to play down a failure in England's Covid-19 testing data system that delayed 15,841 results, saying the much higher updated figures were more in line with forecasts of the outbreak's spread, Reuters reported.

But the glitch is likely to cast further doubt over Johnson's handling of the coronavirus pandemic: his Conservative government's response has been cast by political opponents as slow, poorly organised and confusing.

“The incidence that we're seeing in the cases really sort of corresponds to pretty much where we thought we were,” Johnson said, speaking to reporters.

“To be frank, I think that the slightly lower numbers that we'd seen didn't really reflect where we thought that the disease was likely to go, so I think these numbers are realistic,” said Johnson.