Boris Johnson and Rishi Sunak will now self-isolate after being ’pinged’ by NHS Test and Trace — having initially said they would not.
Downing Street said earlier on Sunday the pair were set to take part in a ‘daily testing’ pilot which meant they would still be able to work.
However it has now been confirmed that they will instead self-isolate.
The government U-turn comes the day before ‘freedom day’ — when most legal coronavirus restrictions come to an end in England.
Mr Johnson and Sunak had both been told to isolate after holding lengthy meetings with Health Secretary Sajid Javid on Friday.
That evening, Mr Javid said he felt ‘groggy’, and completed both a lateral flow and PCR test — which both came back positive for Covid-19.
That prompted NHS Test and Trace to ‘ping’ the Prime Minister and Chancellor, a Downing Street spokesperson confirmed.
Now, having initially said that the ministers would not have to self-isolate, a spokesperson confirmed the duo will do so, just hours after the government’s initial statement.
A No10 spokesman said: "The Prime Minister has been contacted by NHS Test and Trace to say he is a contact of someone with Covid.
"He was at Chequers when contacted by Test and Trace and will remain there to isolate. He will not be taking part in the testing pilot.
"He will continue to conduct meetings with ministers remotely.
"The Chancellor has also been contacted and will also isolate as required and will not be taking part in the pilot."
Rishi Sunak also tweeted: “Whilst the test and trace pilot is fairly restrictive, allowing only essential government business, I recognise that even the sense that the rules aren’t the same for everyone is wrong.
“To that end I’ll be self isolating as normal and not taking part in the pilot.”
The decision to enroll on the pilot attracted criticism from Labour leader Sir Keir Starmer, who said: “Boris Johnson should be setting an example.
“Instead, he gives himself and his Chancellor preferential treatment. It’s a slap in the face to everyone who has made sacrifices to self isolate.
“It can't be one rule for the Conservatives and another for everyone else.”
Elsewhere, Communities Secretary Robert Jenrick also revealed that the current wave of Covid infections may not peak until ‘early September’.