A No 10 spokesman confirmed that ministers were supposed to wear a mask while travelling in their Government cars.
However, the spokesman insisted the Prime Minister had put his mask on “shortly after” he got in the vehicle.
He was getting into the car and, in line with the guidance, put his mask on very shortly afterwards
No 10 spokesman
Mr Johnson had been at Wembley with his wife, Carrie, to cheer on England in their 2-1 victory over Denmark on Wednesday evening.
Photographs of their departure in Mr Johnson’s ministerial Range Rover showed that while Mrs Johnson, his driver and his security detail were all masked, the Prime Minister’s face was uncovered.
The spokesman said: “He was getting into the car and, in line with the guidance, put his mask on very shortly afterwards.”
Asked if ministers were supposed to wear masks in their official vehicles, the spokesman said: “That is the guidance, yes.”