The weekly rate of new Covid-19 cases has soared in dozens of areas of England, following the addition of nearly 16,000 cases that went unreported because of a technical error with an Excel spreadsheet.
Manchester now has the highest rate in England, with 2,740 cases recorded in the seven days to October 1 - the equivalent of 495.6 cases per 100,000 people, up from 223.2 in the previous week.
The problem has led to a delay in efforts by NHS Test and Trace to find the contacts of those who tested positive for the virus, in some cases by around a week.
Prime Minister Boris Johnson was unable to say on Monday morning how many contacts of positive coronavirus cases had been missed.
Liverpool has the second highest rate, up from 287.1 to 456.4, with 2,273 new cases and Knowsley in Merseyside is in third place, up from 300.3 to 452.1, with 682 new cases.
Other areas that saw a jump in cases were:
Newcastle upon Tyne up from 256.6 to 399.6 per 100,000, with 1,210 new cases
Nottingham up from 52.0 to 283.9 per 100,000, with 945 new cases
Leeds up from 138.8 to 274.5 per 100,000, with 2,177 new cases
Sheffield up from 91.8 to 233.1 per 100,000, with 1,363 new cases
Of all the places that have seen a jump in infections when the missing cases were factored in, Manchester, Liverpool, Knowsley and Leeds are all currently subject to local lockdowns.
Sheffield was moved up from the government's area of concern list last week to an area receiving enhanced support.
Test and Trace and Public Health England joint medical adviser, Susan Hopkins, said the issue had not prevented people receiving their test result or affected decision-making in local areas.
All figures are based on Public Health England data published on Sunday night.Mr Johnson said the updated figures meant that the prevalence of the virus was where experts had expected it to be and it would soon be apparent if extra restrictions for some parts of the country were having the intended impact.
The prime minister said: “The incidence that we are seeing in the cases corresponds to pretty much where we thought we were.
“And, to be frank, I think that the slightly lower numbers that we’d seen, you know, didn’t really reflect where we thought the disease was likely to go, so I think these numbers are realistic.
“The crucial thing is that in the next few days, week, we’ll see more clearly whether some of the restrictions that we put in – the extra enforcement of the rule of six, the extra enforcement of self-isolation, the rules on masks and so on – all the stuff that has come in, we’ll see whether that starts to work in driving down the virus.”
He said if people followed the guidance “I have no doubt that we will be able to get on top of it, as indeed we did earlier this year”.
Work and Pensions Secretary Therese Coffey conceded that some people may have been infected with coronavirus because a Test and Trace failure meant nearly 16,000 cases went unreported.
Asked if some could have become infected because of the error, she told Sky News: “There may well be, and I’ve been made aware that probably the majority of that (contact tracing) has happened in the latest element of the week, in the last couple of days."
Labour said the failure to record almost 16,000 positive Covid-19 cases was “shambolic”.
The updated figures mean the UK has now recorded over half a million coronavirus cases.