The UK's coronavirus lockdown will continue for at least another three weeks, and all restrictions will be extended until early May, Dominic Raab, the first secretary of state, announced on Thursday.

This means British people will continue to be barred from leaving their homes apart from a limited number of essential activities, and businesses will remain closed.

Raab also set out five tests for relaxing the lockdown next month.

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The UK's lockdown will continue for at least another three weeks, Prime Minister Boris Johnson's government announced on Thursday.

Other European countries have begun to wind back their lockdown measures as their number of new coronavirus cases flattens.

But Dominic Raab, the UK's first secretary of state, said the country's strict social-distancing measures introduced last month must be extended until at least early May.

Raab, who is deputising for Johnson while he recovers from COVID-19, said any attempt to lift the UK's lockdown measures would lead to a significant increase in coronavirus cases and deaths.

"The very clear advice we've received is that any change to our social-distancing measures now would risk a significant increase in the spread of the virus," he said at a press conference at Downing Street.

"That would threaten a second peak of the virus and substantially increase the number of deaths. It would undo the progress that we've made to date and, as a result, would require an even longer period of the more restrictive social-distancing measures," he said.

Raab added: "Based on this advice, which we very carefully considered, the government has decided that the current measures must remain in place for at least the next three weeks."

He called on Brits to remain "patient," adding that "this is not the moment to give the coronavirus a second chance."

Raab: 'We've lost too many loved ones ... to ease up now'

Johnson's government introduced the lockdown on March 23 as the COVID-19 virus spread across the country.

Under the guidelines, Brits are allowed to leave their homes only for essential reasons, and many businesses are closed. There is also a ban on large public gatherings.

Raab on Thursday set out five tests that must be met before the lockdown measures could be dropped:

The UK "must protect" the National Health Service's "ability to cope." There must be "a sustained and consistent fall in the daily death rates." Official data must show "that the rate of infection is decreasing to manageable levels across the board." Testing and NHS protective capacity must be able to meet future demand after restrictions are lifted. Officials must be confident that any lifting of restrictions will "not risk a second peak of infections that overwhelm the NHS."

The lockdown measures have led to a dramatic drop in the number of people using vehicles and public transport and an apparent flattening of the number of new COVID-19 cases.

In a press conference on Wednesday, Angela McLean, the deputy chief scientific adviser, said there was clear evidence of a "flattened curve" in the number of new cases.

Chris Whitty, the chief medical officer for England, said that the UK was "probably reaching the peak overall."

However, the UK's coronavirus death toll has continued to rise — 13,729 people have died as of Thursday — and one scientific adviser to the government, Jeremy Farrar, said over the weekend that the UK could become "one of the worst if not the worst affected country in Europe."

David King, the UK's former chief scientific adviser, this week also criticised the UK government's slow response to the crisis.

"Why we didn't respond so much sooner once this epidemic broke out in China I simply don't know," said King, who advised the UK government from 2000 to 2007.

"And I say this because in 2006 we published a report on actions needed to deal with a pandemic, and in that report we showed that if an outbreak occurred of any new virus of this kind, anywhere in the world, within three months, due to air travel, it would be everywhere in the world. And that, of course, is what has happened — and it seems that we were unprepared, and we didn't take action."