British Prime Minister Boris Johnson is not on a ventilator but has had some oxygen support and if his condition changes the government will make an official statement, Cabinet Office Minister Michael Gove said on Tuesday.

"He's not on a ventilator no," Gove told LBC radio. "The prime minister has received some oxygen support and he is kept under, of course, close supervision."

Foreign Secretary Dominic Raab will run the country and any decision on lifting coronavirus lockdown restrictions won't be delayed, Gove said.

"The person who is running the country, following the plan that the prime minister has set out, is Dominic Raab, the foreign secretary," Gove said on ITV.

Asked if a decision on changing lockdown restrictions, due to be reviewed on Monday, would be put off, Gove said: "No it won't be delayed. It will be the case that we will take that decision collectively as a cabinet... the person who will make the final decision is... the foreign secretary."