BORIS Johnson is expected to unveil a coronavirus warning system when he outlines his plans to gradually ease the lockdown while dropping the "stay home" slogan.

The Prime Minister will instead tell the country to "stay alert, control the virus and save lives" when he outlines his "road map" to a new normality during an address to the nation tonight (Sunday, May 10).

Mr Johnson is planning to urge workers who cannot do their jobs from home to begin returning to their workplaces while following social-distancing rules.

"This is the dangerous bit," he warned ahead of the announcement.

It is understood that a warning system administered by a new "joint biosecurity centre" will detect local increases in infection rates, with the view to locally alter restrictions in England.

With the alerts ranging from green in level one to red in level five, Mr Johnson is expected to say the nation is close to moving down from four to three.

The PM will chair a meeting of the emergency Cobra committee with Cabinet ministers, leaders of the devolved nations and London Mayor Sadiq Khan before his 7pm pre-recorded address.

On Monday, the Government will publish a 50-page document outlining the full plan to cautiously re-start the economy to MPs after figures suggested the overall death toll for the UK has passed 36,500.

The shift in messaging will come amid concerns that workers may not feel comfortable resuming their roles after the weeks of firm instructions to "stay at home, protect the NHS, save lives".

That could be a test for ministers, with unions warning that they might not recommend their millions-strong membership to resume their roles if safety is not assured.

"The trade union movement wants to be able to recommend the Government's back-to-work plans," Unison, Unite, the GMB, Usdaw and the Trades Union Congress wrote in a letter to the Observer.

"But for us to do that we need to ensure that ministers have listened and that we stay safe and save lives at work too."