Prime Minister Boris Johnson says he is confident the UK can "turn the tide" of Covid-19 in the next 12 weeks, but only if people follow government advice.

Summing up the conference, Mr Johnson said his message to companies is "really think very carefully before you start laying off your staff".

He added: "We do want to stand behind good companies, we do want to make sure people recognise that if they stand behind their staff, they should stand behind their staff, because we in the Government are going to stand behind British firms.

In Downing Street’s latest daily televised press conference he thanked the country for its "huge efforts" to comply with the government's advice.

He has been joined once again by the UK’s chief medical adviser, Prof Chris Whitty, and chief scientific adviser, Sir Patrick Vallance.

Mr Johnson said "we can turn the tide within the next 12 weeks", adding: "I'm absolutely confident we can send the virus packing in this country."

Trials on a vaccine were expected to begin within a month, he said.

"By the same token we're massively increasing the testing to see whether you have it now and ramping up daily testing from 5,000 a day, to 10,000 to 25,000 and then up at 250,000." he explained.

No plans to stop the London tube network was confirmed but the capital will see tougher measures if people did not do more.

It is vital that people follow that advice," said the Prime Minister. "There is huge evidence that they are (social distancing) in the takings of the retail sector, the hospitality sector, TfL (Transport of London) in inner London down about 50 per cent, in outer London 60 per cent.

"But some evidence that in parts of the capital it is very patchy and some areas where people aren't following it in quite the way we need them to do," he said.

Mr Johnson acknowledged there had been some "misunderstanding" over the Government's plans.

"There is no prospect of us wanting to stop public transport in London or stop the Tube or the buses," he said. "We are going to want people to avoid gatherings where they transmit the disease. If it becomes necessary to do more to ensure that, we will certainly do so."

Speaking alongside the PM, Prof Chris Whitty, the UK's chief medical adviser, warned there would be a "lag" before the public's efforts to stem the spread of the virus would slow down case numbers.

"The first thing that will get under the greatest pressure will be intensive care and respiratory care system, that's the first point of real pressure on the NHS that's going to be happen, he explained.

"And to be clear: even if everybody does all the things we hope and really, really would ask that they will do, the numbers will continue to go up over the next two weeks because there's a lag until things start to improve."

Daily press conferences held at 10 Downing Street Covid-19 was also raised which could be conducted "remotely" in the near future.

"We may have to find some way of getting them done in a way that doesn't look to everybody else as though we are not following the advice that we give the public," said Mr Johnson.

"I know that you are all sitting a long way away from each other, but it may be that we need to do more social distancing."

Emphasis was also made for businesses to avoid making employees redundant as more companies announce partial closures and reduced hours due to lack of work.

"I know how difficult it may be or it may seem right now, but if we do this together, we will save as I say many, many thousands of lives," the PM said. "I say to business, stand by your employees, stand by your workers, because we will stand by you."