A protester holds a sign at an anti coronavirus lockdown protest in Old Market Square, Nottingham, England, after a range of new restrictions to combat the rise in coronavirus cases came into place in England, Saturday, Oct. 3, 2020. (Danny Lawson/PA via AP)

The British government faced huge questions Monday over its coronavirus testing system after a technical glitch led to the under-reporting of new infections over the past week or so, a failing that could have given fresh impetus to the current outbreak and ultimately to an uptick in deaths.

Health Secretary Matt Hancock is due to make a statement to lawmakers later Monday after the opposition Labour Party asked the government to explain why the cases were not tabulated when they should have been.

The latest problems to afflict the U.K.'s test and trace program emerged over the weekend when public health officials revealed that a total of 15,841 virus cases weren't tabulated from Sept. 25 to Oct. 2.

The government said the "technical issue" was discovered Friday night and has now been resolved. The problem is thought to have stemmed from file limitations on the Excel spreadsheets that the government used for its test and trace program.

The unreported cases were added to the government's daily new infections total over the weekend, boosting Saturday's number to 12,872 cases and Sunday's to 22,961.

The number of new cases reported Monday fell sharply to 12,594, but given the adjustments related to the missing cases, it's difficult to make direct daily comparisons. Before the glitch was identified, there had been signs that the number of new infections had been leveling off around the 7,000 a day mark, which Britain hit the preceding four days.

People ride a Northern Line train in London after the 10 p.m. curfew pubs and restaurants are subject to in order to combat the rise in coronavirus cases in England, on Saturday Oct. 3, 2020. (Victoria Jones/PA via AP)

While all of those who tested positive were informed of the results, Public Health England said their contacts had not been traced.

For the test-and-trace program to work well, contacts should be notified as soon as possible. So authorities' failure to inform people potentially exposed to the virus could lead to many more positive cases and the need for the government to impose further unwanted restrictions on everyday life.

Jonathan Ashworth, Labour's spokesman on health issues, described the error as "shambolic'' and said the public "will be understandably alarmed.''

He said Hancock should tell lawmakers "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."

The reporting error is just the latest problem with Britain's test and trace system, which is seen as crucial to slowing the spread of COVID-19 and reducing the need for further limits on social interaction. Lawmakers from all parties have previously criticized Prime Minister Boris Johnson's Conservative government for a shortage of testing capacity and delays in notifying people of their test results.

Britain's Prime Minister Boris Johnson arrives at BBC Broadcasting House to appear on the Andrew Marr show, in London, Sunday, Oct. 4, 2020. Johnson has defended his handling of the coronavirus pandemic, but warned that the country faces a "bumpy" winter ahead. Britain has Europe's highest coronavirus death toll, at more than 42,000, and Johnson's Conservative government is facing criticism from all sides. Opponents say tougher social restrictions are needed to suppress a second pandemic wave. (Victoria Jones/PA via AP)

Paul Hunter, a professor in medicine at the University of East Anglia, said the news about the glitch is "very disappointing."

"For the test, track and trace system to have a real impact on reducing transmission of COVID-19, it is essential that test results are communicated rapidly," he said.

Like other countries in Europe, the U.K. has seen rising coronavirus infections over the past few weeks, which has prompted the government to announce a series of restrictions, both nationally and locally, to keep a lid on infections. They are largely centered on limiting the number of people allowed to gather together and putting a curfew on pubs in order to suppress the virus.

The U.K. has Europe's highest virus-related death toll at more than 42,400. The government's chief scientific advisers warned two weeks ago that the number of new cases in the U.K. could be doubling every week or so if no action was taken and that the country could end up with 50,000 new cases a day by the middle of October, leading to hundreds of daily deaths a month later.

  • Signage at an anti coronavirus lockdown protest in Old Market Square, Nottingham, England, after a range of new restrictions to combat the rise in coronavirus cases came into place in England, Saturday, Oct. 3, 2020. (Danny Lawson/PA via AP)

  • People enter Oxford Circus underground station in London on Friday, Oct. 2, 2020, after the 10 p.m. curfew that pubs and restaurants are subject to in order to combat the rise in coronavirus cases in England. (Kirsty O'Connor/PA via AP)

  • A worker packs away chairs outside a bar in Soho, London, ahead of the 10pm curfew pubs and restaurants are subject to in order to combat the rise in coronavirus cases in England, Friday, Oct. 2, 2020. (Kirsty O'Connor/PA via AP)

The confusion over the daily testing numbers only adds to the uncertainty over whether the restrictions are working in suppressing the virus.