Boris Johnson ordered the dramatic closing down of the hospitality and entertainment sectors amid fears the NHS will be overwhelmed unless the Covid-19 outbreak is checked.

With scientists warning "social distancing" measures will have to stay in place for months to come, cinemas, nightclubs, gyms and betting shops were left wondering they would be able to open their doors again.

Meanwhile economists have said the bill to taxpayers for the Government's unprecedented scheme to cover most of the wages of workers whose jobs are under threat from the outbreak could run to billions of pounds a month.

The Prime Minister announced the closure of pubs and restaurants at a Downing Street news conference on Friday following reports that many people were ignoring an earlier voluntary appeal to stay away.

While he acknowledged the ban went against the "freedom-loving instincts" of the British people, he said it was essential to achieve the 75% reduction in "unnecessary" social contacts required to reduce the rate of infection.

It was not clear exactly how the measures - backed by the devolved administrations in Scotland, Wales and Northern Ireland - will be enforced, although the Prime Minister indicated it could be done through the licensing system.

The move came as a further 39 people in England were confirmed to have died after testing positive for Covid-19, bringing the UK death toll to 177.

Mr Johnson said there was a "massive effort" underway to ensure the health service had the ventilators and intensive care beds to cope with the expected influx of new hospital cases.

Doctors in Italy, where the death toll has topped 4,000, warned the NHS to expect a "tsunami" of patients as the number of people needing specialist hospital treatment surged.

Number 10 said in a statement that Mr Johnson spoke with UN Secretary-General Antonio Guterres about the "need for a global response" to the pandemic, which Mr Guterres had earlier warned could cause a global recession 'perhaps of record dimensions'.

In a sign of the pressures that are building, it emerged that a major London hospital temporarily declared a "critical incident" on Thursday due an upsurge in coronavirus admissions.

In a message to staff, Northwick Park Hospital in Harrow said that it did not have enough space for patients requiring critical care.

Meanwhile the Institute of Fiscal Studies (IFS) warned the cost of Chancellor Rishi Sunak's coronavirus job retention scheme was simply "unknowable".

In a move previously unthinkable for a Conservative government, he said employers would be able to apply to HM Revenue and Customs to cover 80% of the wages of staff they keep on up to GBP2,500 ($A5027) a month.

Australian Associated Press