Britain reported a jump in daily COVID-19 cases to a record 22,961 on Sunday, after authorities said a technical issue had meant that over 15,000 test results had not been logged in online.
News of the glitch was likely to cast further doubt over the robustness of the national test-and-trace system, which Prime Minister Boris Johnson said would be "world-beating" but which has experienced a series of delays and setbacks.
Sunday's daily cases figure represented a dramatic jump from the 12,872 cases reported on Saturday. The Sunday numbers were published hours behind schedule, just after a statement from Public Health England (PHE) about the technical problem.
"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.
The technical problem, which was identified on Friday and has now been resolved, led to 15,841 cases not being uploaded into reporting dashboards used by the National Health Service (NHS) contact-tracing system.
"We fully understand the concern this may cause and further robust measures have been put in place as a result," said PHE's interim chief executive, Michael Brodie.
The authority said that all the people concerned had been given their results in a timely fashion, and that those with positive results had been told to self-isolate.
In terms of tracing the contacts of the infected people, PHE said the information had been transferred to the relevant systems over the weekend and contact tracers were now working urgently to catch up.
"NHS Test and Trace have made sure that there are more than enough contact tracers working, and are working with local Health Protection Teams to ensure they also have sufficient resources to be urgently able to contact all cases. We are also increasing the number of call attempts from 10 to 15 over 96 hours," PHE said.