• Government adviser says lockdown needed until end May
• Another adviser questions national shutdown strategy
• Britain's coronavirus death toll stands at 3,605

LONDON: Britain is unlikely to lift its stringent lockdown rules until the end of May, a leading government adviser said on Saturday, warning that the spread of coronavirus must first slow and intense testing be introduced.

The government has put Britain into a widespread shutdown, closing pubs, restaurants and nearly all shops, while ordering people to stay home unless absolutely essential to venture out.

The order is designed to curb the spread of COVID-19 in the country, which has almost 40,000 confirmed cases and 3,605 deaths, but some experts have started to question whether the shuttering of the economy will cost more lives in the long run.

"We want to move to a situation where at least by the end of May we're able to substitute some less intensive measures, more based on technology and testing, for the complete lockdown we have now," Neil Ferguson, a leading professor of mathematical biology at Imperial College London, told BBC Radio.

Britain initially took a restrained approach to the outbreak but Prime Minister Boris Johnson changed tack and imposed stringent social-distancing measures after Ferguson's modelling showed a quarter of a million people in the country could die.

The response has since been hampered by a lack of ventilators and an inability to carry out mass testing to determine whether the public, and particularly health workers, have built up an immunity.

A second senior government adviser, the chief pandemic modeller Graham Medley, said he feared Britain had painted itself into a corner, with no clear exit from a strategy that would damage the economic and mental well-being of many people.

Almost one million people have applied for welfare benefits in just two weeks in Britain, according to official data that shows the economy is set for a depression that could be worse than the slump in the 1930s.

"If we carry on with lockdown it buys us more time, we can get more thought put into it, but it doesn't resolve anything - it's a placeholder," Medley told the Times newspaper.

"We've kind of painted ourselves into a corner, because then the question will be, what do we do now? In broad terms are we going to continue to harm children to protect vulnerable people, or not?"

Health minister Matt Hancock has set a goal of 100,000 tests per day by the end of this month, a tenfold increase that industry leaders have questioned due to shortages of specialist chemicals and testing kits. It is also considering immunity certificates.

Medley said the antibody tests could help but were not working so far.

Separately the government said it would free prisoners who were deemed to be low risk and were within weeks of release.