The SNP's Ian Blackford has launched a scathing attack against top government aide Dominic Cummings after reports suggest he broke lockdown restrictions while experiencing coronavirus symptoms.

The party's Westminster leader demanded answers from Prime Minister Boris Johnson over Cummings' trip, where he is reported to have travelled 200 miles from London to Country Durham to visit his parents.

Blackford said the PM has 'serious questions' to answer, in light of more reports suggesting members of Downing Street were aware of the flouting, and says it now appears to be a 'cover-up'.

READ MORE: Calls for Cummings to resign after claims he broke lockdown rules in 260-mile journey from London to Durham

“I think what should have happened by now is that Dominic Cummings should have gone," Blackford told BBC Radio 4's Today programme. "What I find interesting…is that (according to some reports) members of Downing Street knew about this so, first and foremost, Boris Johnson has serious questions to answer over what now appears to be a cover-up.

"The Prime Minister must explain exactly when he knew about the breaking of the rules, whether he sanctioned it, why Cummings wasn’t sacked immediately and why it appears that he tried to cover it up, not telling the public until the newspaper(s) broke the story eight weeks later last night.”

Blackford branded the alleged actions the “height of irresponsibility for someone to think this is a reasonable course of action”, and added: “Here we have the highest official in Government, the closest confidant of the Prime Minister prepared to break the rules that the rest of us are being asked to obey.

“You cannot have a situation where there appears to be one rule for the powerful and the millions of the rest of the public are being told we must follow Government advice. Demonstrably, this is an individual who has broken the advice he has been, in many cases, the architect of delivering.”

Mr Blackford said Mr Cummings’ alleged actions were “more serious breaches” than rule-breaking carried out by UK Government adviser Professor Neil Ferguson and former Scotland chief medical officer Catherine Calderwood, both of whom resigned for their breaches.

He is not the only politician to call for Cummings' resignation.

Sir Ed Davey, acting leader of the Liberal Democrats, said: "If Dominic Cummings has broken the lockdown guidelines, he will have to resign, it is as simple as that."

READ MORE: The high-profile figures who have breached lockdown restrictions 

Labour, meanwhile, said No 10 needed to issue a "very swift explanation" about what went on.

A party spokesman said: "If accurate, the Prime Minister's chief adviser appears to have breached the lockdown rules. The Government's guidance was very clear: stay at home and no non-essential travel.

"The British people do not expect there to be one rule for them and another rule for Dominic Cummings."