It is "unfair and unnecessary" for people to ask the government's scientific advisers about the Dominic Cummings row, Boris Johnson has claimed.
It comes as Durham Police confirmed the PM's top aide may have breached lockdown rules when he drove to Barnard Castle from his parents' property in Durham in March, but said they would not be taking further action over the matter.
Appearing alongside Johnson at Thursday's coronavirus briefing, Sir Patrick Vallance, the government's chief scientific adviser, was asked for his view on the matter.
But the prime minister told journalists: "I know you've asked Chris [Whitty] and Patrick but I’m going to interpose myself if I may and protect them from what I think would be an unfair and unnecessary attempt to ask a political question.
It's very, very important that our medical officers and scientific advisers do not get dragged into what most people would recognise is fundamentally a political argument."
Johnson said he had said "quite a lot on this matter already and what I also note is that the Durham Police said was they were going to take no action and that the matter was closed".
"I intend to draw a line under the matter, as I said I think yesterday to the parliamentary Liaison committee," he added.