Johnson said the government could not yet spell out how changes to the lockdown policy would be implemented – or how quickly.

“We simply cannot spell out now how fast or slow, or even when, those changes will be made,” he said.

“Clearly the government will be saying much more about this in the coming days.

“These decisions will be taken with the maximum possible transparency.”

Johnson returned to work on Monday under significant pressure to map out an exit strategy from lockdown restrictions, and to answer questions about a shortfall in testing in the UK.