Dominic Cummings “clearly undermined” the public health advice with his lockdown trip to County Durham, the former civil service boss has said.

Ex-Cabinet Secretary Mark Sedwill said it was a “mistake” for the Prime Minister’s top aide to make the 260-mile trip after his wife developed coronavirus symptoms in March.

While Boris Johnson said Mr Cummings had acted “reasonably”, Lord Sedwill said the move had caused public compliance with Government’s coronavirus restrictions to crumble.

“It was clearly a difficult moment for the Government,” he told the BBC.

“It was a mistake – whether everyone should quit every time they make a mistake, I don’t think is right.