There has been a delay in nearly 16,000 positive coronavirus results being added to the official figures, the government has announced.
It comes as a further 22,961 lab-confirmed cases of the coronavirus were recorded in the UK, taking the total number to more than 500,000 since the outbreak began.
The government said that, due to a technical issue, there had been a delay in publishing 15,841 cases in England, meaning the total reported over the coming days will include some additional cases from between 25 September and 2 October.
Public Health England (PHE) said the people involved all received the test results and those who tested positive were advised to self-isolate.
"Today and yesterday's headline numbers are large due to the backlog of cases flowing through the total reporting process," PHE said in a statement.
And joint medical director Dr Susan Hopkins told Sky News: "There's no delay in people receiving their test results.
"The delays are in reporting to the dashboard and to the public and there's been a delay in contact tracing initiation.
"Public Health England apologise that this occurred and have put in place steps to prevent this happening again."
Speaking earlier, the prime minister admitted there had been a "failure in the counting system" and that the issue was not ongoing.
"All the people who had a positive test have now been notified and I think the data that we have is realistic, and again it's very useful in helping us to identify you know where the incidence is and what we need to do to tackle it," he said in an interview with the BBC's Andrew Marr Show.
Northern Ireland secretary Brandon Lewis said the revisions were evidence of the government and NHS Test and Trace being "transparent" about the testing numbers.
He told Sophy Ridge on Sunday: "As soon as they've spotted there was an issue, they've dug into that, they've got to the bottom of those numbers, they have been transparent and published the correct numbers and of course the teams will be looking through that to ensure it doesn't happen again."
However, Labour said the failure to record almost 16,000 positive COVID-19 cases was "shambolic".
Shadow health secretary Jonathan Ashworth said: "This is shambolic and people across the country will be understandably alarmed.
"Matt Hancock should come to the House of Commons on Monday to explain what on earth has happened, what impact it has had on our ability to contain this virus and what he plans to do to fix test and trace."
PHE provided a breakdown of how many cases were not included in each day's figures, which are as follows:
957 cases on September 25, when the original figure given was 6,874
744 on September 26, when the original figure given was 6,042
757 on September 27, when the original figure given was 5,693
None on September 28, when the original figure given was 4,044
1,415 on September 29, when the original figure given was 7,143
3,049 on September 30, when the original figure given was 7,108
4,133 on October 1, when the original figure given was 6,914
4,786 on October 2, when the original figure given was 6,968
He acknowledged there will be some members of the public who are "furious at me" and "furious at the government" amid the continuing COVID-19 restrictions.
"I've got to tell you in all candour it's going to continue to be bumpy through to Christmas, it may even be bumpy beyond."