Johnson, 55, said he still has a temperature, one of the symptoms associated with coronavirus, and would therefore have to stay in isolation for longer.
“Although I’m feeling better and I’ve done my seven days of isolation, alas I still have one of the symptoms, a minor symptom.
“I still have a temperature and so, in accordance with the government advice, I must continue my self-isolation until that symptom itself goes,” Johnson said in a new video message.
He used the latest message to urge the British public to stay at home ahead of the weekend, during which warmer weather is forecast after days of cold.
He said: “I just want to say one crucial thing, one quick thing to everybody thinking about this weekend and what may be some fine weather.
“Because I reckon a lot of people will be starting to think that this is all going on for quite a long time, and they’d rather be getting out there and, particularly if they’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, he said.
“And 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. Let’s stick with it now,” the prime minister said.
Johnson was last seen, still looking quite poorly, when he made a brief appearance at Downing Street on Thursday night to join the national “clap for carers” applause in appreciation of the hardwork of National Health Service (NHS) workers on the frontline of the fight against the outbreak.
“Remember that incredible clapping again last night for our fantastic NHS. We’re doing it to protect them and to save lives. et’s focus on doing everything we can. Stay at home folks, protect our NHS, save lives,” he said.
Johnson has been leading video conferences and virtual Cabinet meetings from his private quarters, the flat above No.11 Downing Street — traditionally used by Prime Ministers as their home next door to their No.10 office.
His pregnant fiancée Carrie Symonds has been self-isolating separately at her flat in south London with their dog Dilyn.
The prime minister revealed his COVID-19 diagnosis last Friday, when he said he had tested positive for coronavirus after developing mild symptoms but vowed to remain in charge of the country’s fightback against the pandemic.