SNP Westminster leader Ian Blackford has called on the head of the civil service to investigate the "rule-breaking and the Tory Government's cover-up" of Dominic Cummings' lockdown journey to Durham.
The Prime Minister's top aide has come under fire after it emerged he had driven 250 miles despite the guidelines on travelling - and showing symptoms of coronavirus.
In the letter to Sir Mark Sedwill and Boris Johnson, Mr Blackford highlights the "matter of serious public concern" with several questions for the PM including when he found out about the trip and what role the UK Government played in "keeping the public in the dark for eight weeks".