Boris Johnson is to remain in self-isolation despite completing the planned seven-day period, as he continues to have a high temperature.

In a message on Twitter, the prime minister said he was extending his period of isolation in line with medical guidance.

And he issued an appeal to the public to stay at home over the coming weekend, when good weather is forecast, in order to “protect the NHS and save lives”.

He acknowledged that many people - particularly those with children in their households - may be feeling "stir crazy" after almost a fortnight behind closed doors.

But he urged them to maintain their "brilliant" efforts to reduce social contacts which he said had helped slow the spread of the disease.

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And he told them: "Let's focus on doing everything we can - stay at home folks, protect the NHS, save lives.”

Mr Johnson, who was clearly not in full health in the brief video message, said: “Although I’m feeling better and I have done my seven days of self-isolation, alas I still have one of the symptoms – a minor symptom. I still have a temperature.

“So, in accordance with government advice I must continue my self-isolation until that symptom goes.”

Mr Johnson had hoped to come out of isolation on Friday, having confined himself to his flat and an 11 Downing Street study and office after showing symptoms of coronavirus on 26 March.

Number 10 said he was complying with medical advice that anyone with symptoms should self-isolate for seven days, or longer if their high temperature persists.

No new date was named for Mr Johnson to emerge. He has continued to chair meetings of cabinet and the daily Covid-19 committee by video link, and appeared at the door on Thursday evening to join national applause for NHS workers.

The PM’s official spokesman declined to say how high Mr Johnson’s temperature was, but said: “The guidance is very clear and the prime minister is following that advice to the letter. That is what we are expecting the public to do, and it’s absolutely right that the prime minister should follow that advice too.”

In a message to anyone tempted to break social distancing guidance to enjoy the fine weather this weekend, Mr Johnson said: “I reckon a lot of people will be starting to think that this is all going on for quite a long time and would rather be getting out there, particularly if you’ve got kids in the household.

"Everybody may be getting a bit stir crazy, and there may be just a temptation to get out there, hang out and start to break the regulations.

“I just urge you not to do that. Please, please, stick with the guidance now.

“This country has made a huge effort, a huge sacrifice, done absolutely brilliantly well in delaying the spread of the virus.