THE rising covid-19 case numbers are now "flashing like warnings in a passenger jet", the Prime Minister has said.

Boris Johnson made the comparison at a press conference at which he announced England's new three-tier system for tackling the spread of the virus.

"The number of cases has gone up four times in four weeks," he said this evening. "It is once again spreading among the elderly and the vulnerable and deaths are also rising once again.

"We must act now."

Mr Johnson said the Nightingale Hospitals in the North of England are being prepares for service and the Government is giving extra funding to local authorities across England to protect vital services.

Explaining the tier system, he said there will be three level; medium, high and very high.

Areas in the very high tier - which from Wednesday will include Liverpool city region - will be reviewed every four weeks.

Those living in areas on the most severe level of restrictions will have all of the current national regulations, as well as a package of measures worked out with local leaders as well as tailored support.

Mr Johnson said these would be "at minimum a ban on all social mixing between households in private places including gardens."

The minimum measures will also see pubs and bars close unless they can operate as a restaurant only and people will be asked not to travel into or out of areas in the "very high" tier.

Mr Johnson said the majority of the country will be placed in the medium category at the moment.

Most areas currently under local intervention will be at high, with areas including East and Wast Cheshire also moving to this level.

Medium, Mr Johnson said, will function similarly to existing national measures such as the rule of six and the restriction of alcohol safes at ten.

High will include extra restrictions on indoor social mixing.

Chancellor Rishi Sunak said those in England whose employers are able to continue operating safely but with reduced or uncertain demand would be able to have their wages directly subsidised by the Government over the winter.

People whose employers have been asked to close - if that means they are unable to work for one week or more - will be able to get two thirds of their wage, again covered by the Government.

Businesses in England which are legally required to close will be able to apply for a cash grant.

Professor Chris Whitty, chief medical officer for England, urged the public to follow the guidance.

He said: "If there had not been a real attempt to limit transmission, the rates we're seeing would be substantially higher in my view. "What people are doing now is reducing the rates but we will need to go further or they will continue to rise inexorably."

Asked by a member of the public about what restrictions he envisaged towards Christmas, the Prime Minister said: "We will do our very best to make sure we get as close to normal as possible for Christmas but that is going to depend on out success in getting the virus down and our ability as a country to follow the measures.

"It will mean in those local areas that we're not only going to have to intensify the measures, we're going to have to enforce the social distancing, the guidance of hands, face space and get a test, self isolate if you're contacted by the NHS.

"All that basis stuff is essential if we're going to have anything like a normal Christmas."

Professor Whitty said the way forward entails a delicate balance between two harms; with health in one hand and the economy in the other.

"The idea that we can do this without causing harm is an illusion," he said.

"Every country is struggling with this. It is a balancing act. "We're all trying to find the narrow path between these two harms."

Asked about the message to those who were previously advised to shield, he said: "People who were previously in the shielding group are at greater risk and we would advise them to take greater precautions."

He added further and more detailed advice is expected to be issued on the matter tomorrow.