Britain reported 12,872 new COVID-19 cases on Saturday, almost double the number from a day earlier, with the government blaming the jump on a reporting delay and saying the numbers in coming days would include additional cases.

The government's website said a technical issue had delayed publishing a number of new COVID-19 cases.

"This means the total reported over the coming days will include some additional cases from the period between 24 September and 1 October, increasing the number of cases reported," it said.