Shoppers wear face masks to protect against the coronavirus outbreak as they do their weekend shopping at a supermarket in London, Friday, April 17, 2020. The highly contagious COVID-19 coronavirus has impacted on nations around the globe, many imposing self isolation and exercising social distancing when people move from their homes.(AP Photo/Frank Augstein)

A leading public health expert said Friday that Britain likely has the highest coronavirus death rate in Europe due to what he described as "system errors," while the government defended its record in responding to the pandemic.

Anthony Costello, director of the Institute for Global Health at University College London, said the U.K. "could see 40,000 deaths" by the time the first wave of the country's outbreak is over.

The British government reported that as of Thursday, 13,729 people had died in U.K. hospitals after testing positive for the coronavirus. The number does not include hundreds, and maybe thousands, of virus-related deaths in nursing homes and other settings.

Costello has been a vocal critic of the government's strategy, saying it has not been doing enough testing for the virus and has failed to trace and isolate people who were in contact with infected individuals.

"What were the system errors that led us to have probably the highest death rates in Europe?" he said.

"We're going to face further waves and so we need to make sure we have a system in place ... that enables you to test people rapidly in the community, in care homes and to make sure that the results are got back to them very quickly," Costello told a committee of British lawmakers Friday.

London Ambulance staff, police officers and firefighters take part in the weekly "clap for our carers" as they stand on Westminster Bridge backdropped by a scaffolded Big Ben and the Houses of Parliament in London, during the lockdown to try and stop the spread of coronavirus, Thursday, April 16, 2020. The applause takes place across Britain every Thursday at 8pm local time to show appreciation for healthcare workers, emergency services, armed services, delivery drivers, shop workers, teachers, waste collectors, manufacturers, postal workers, cleaners, vets, engineers and all those helping people with coronavirus and keeping the country functioning while most people stay at home in the lockdown. (AP Photo/Matt Dunham)

NHS staff applaud outside the Chelsea and Westminster Hospital in London during the weekly "Clap for our Carers", Thursday, April 16, 2020. The applause takes place across Britain every Thursday at 8pm local time to show appreciation for healthcare workers, emergency services, armed services, delivery drivers, shop workers, teachers, waste collectors, manufacturers, postal workers, cleaners, vets, engineers and all those helping people with coronavirus and keeping the country functioning while most people stay at home in the lockdown. (AP Photo/Alberto Pezzali)

In this Thursday, April 16, 2020 photo, David Anderson, left, Executive Director for Quality, Infection Prevention and Control at the charity UK-Med trains medical staff on how to put on and remove PPE, personal protective equipment, to avoid being infected or transmitting coronavirus, at the Nightingale Hospital North West set up in the Manchester Central Convention Complex in Manchester, northern England. The complex has been converted into a hospital to provide care for an increased number of patients requiring treatment during the coronavirus pandemic. (AP Photo/Jon Super)

Britain was slower than many other European countries to impose mandatory restrictions on business and daily life to slow the spread of the coronavirus. A lockdown ordered on March 23 was extended Thursday for at least three more weeks. Schools, restaurants and most shops are closed, and most people are allowed to leave home only for essential errands or exercise.

Health Secretary Matt Hancock defended the government's record, saying "test, track and trace" was part of its strategy.

"I think we took the right measures at the right time," he said.

The government vowed to conduct 100,000 coronavirus tests a day by the end of April, a more than five-fold increase on current rates. It has also promised to include nursing home deaths in the official tally.

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