LONDON, MAY 10 – An alert system to rank the threat level of coronavirus in England is set to be launched by the government.

Prime Minister Boris Johnson is expected to unveil the system, which will use a scale of one to five, as part of an address broadcast to the nation at 19:00 BST.

Mr Johnson will also explain any changes to the UK’s lockdown measures.

It comes after he introduced a new slogan telling the public to “stay alert, control the virus, save lives”.

Communities Secretary Robert Jenrick said it was the right time to “update and broaden” the message.

However, the devolved governments in Scotland, Wales and Northern Ireland have said the “stay at home” advice will remain in place.

Mr Johnson is not expected to provide exact dates for when the strict curbs on daily life – which have been in place for seven weeks – might change.

• What to watch for in the PM’s coronavirus speech

The threat level system will apply to England only but the government is working with the devolved administrations as they develop their own.

It is understood the system – with alerts ranging from green (level one) to red (level five) – will be similar to the one used to keep the public informed about the terror threat level.

Mr Johnson is expected to say England is currently at stage four but moving towards stage three.

New slogan ‘needs clarity’

Communities Secretary Robert Jenrick told the BBC’s Andrew Marr Show it was the right time to “update and broaden” the message to the public from “stay at home” to “stay alert”.

“Stay alert will mean stay alert by staying home as much as possible, but stay alert when you do go out by maintaining social distancing, washing your hands, respecting others in the workplace and the other settings that you’ll go to,” he said.

But shadow health secretary Jonathan Ashworth said the government must clarify what the new slogan means.

“When you’re dealing with a public health crisis of this nature you need absolute clarity from government about what the advice is. There is no room for nuance,” he told Marr.

“The problem with the new message is that many people will be puzzled by it,” he added.

The alert tool – to be administered by a new “joint biosecurity centre” – will reflect the virus threat in different parts of the country, meaning the threat level in one city could differ quite widely from another.

This could inform the local alteration of restrictions in England.

A meeting of the government’s Cobra emergency committee involving the cabinet, devolved nations and the mayor of London will be held before Mr Johnson’s televised address on Sunday evening, with the plans to be put before Parliament on Monday.

Mr Jenrick said the UK government’s “strong preference” was for the devolved nations “to move as one”.

The UK government’s new slogan is part of moving into the next phase of the response to coronavirus.

Staying at home where possible will remain part of the strategy, but ministers want to “broaden the message”.

Some are worried the new campaign is ambiguous and muddies the water.

In Wales and Scotland, the devolved governments have made clear they will keep the original slogan – “stay at home, protect the NHS, save lives”.

So from tomorrow, messaging will be different in different parts of the UK.

And I understand there are real concerns in the Scottish government about how people will react – with fears it will be harder to get the public to follow their advice to stay at home unless essential.

The communities secretary also told Marr a contact tracing app being trialled on the Isle of Wight had been downloaded by about 50,000 people.

Asked about reports a second app was being developed, Mr Jenrick said: “We are learning lessons from the other apps that exist elsewhere in the world and if we need to change our app, we will do. That’s the point of piloting this before we take it national.”

‘Best protection is your front door’

Prof Jason Leitch, national clinical director for the Scottish government, told BBC Breakfast he “can’t explain” what the prime minister’s revised message of “stay alert” means.

Prof Leitch reiterated what First Minister Nicola Sturgeon said earlier this week – that the key message for Scotland “remains ‘stay at home'” – and added: “I think the messaging is really important…. the best protection for this virus is your front door. There isn’t any question about that.”

On Saturday, Transport Secretary Grant Shapps warned the government would proceed with “extreme caution” when lifting lockdown measures.

Mr Ashworth said while the lockdown remains important, it is “fundamentally a blunt tool” with “huge societal problems” building the longer it continues.

Meanwhile, a model of protective goggles is being withdrawn from hospitals and care providers because they do not meet standards for coronavirus settings, the government has said.