Boris Johnson has been urged to condemn Dominic Cummings' "continued flouting of the rules" after he "fatally undermined public health messaging" with his lockdown trip to Durham.
Labour MP Mary Kelly Foy challenged the Prime Minister over the conduct of his top aide, who travelled to County Durham at the height of the first lockdown.
While there, he famously made an ill-advised trip to Barnard Castle, around 30 miles away, on his wife's Mary Wakefield's birthday on April 12.
Mr Cummings claimed that he was checking to see if his eyesight was good enough to make a longer drive back to London.
Ms Foy, the City of Durham MP also raised the row over a backdated council tax for two properties, including Mr Cummings' 'lockdown cottage' at the family farm near Durham, which were built in breach of planning regulations.
© PABoris Johnson was challenged over the conduct of his aide Dominic Cummings
Speaking during Prime Minister's Questions, she said: " Dominic Cummings has fatally undermined public health messaging, has historic planning violations exposed and has shortchanged us with an unpaid council tax bill of up to £50,000.
"Will the Prime Minister condemn this continued flouting of the rules or does he have a blind spot that even a trip to Barnard Castle can't fix?"
Mr Johnson dismissed her questions and claimed the public health message had been undermined by "constant party political point scoring".
He said: "I think what has undermined people's confidence and understanding of what the Govt is trying to do is constant party political point scoring and attempts to obscure what we are trying to do by the Labour Party."
He urged her to advise her constituents to follow the guidance to get the virus down, adding: "Let's all do this together."
Mr Cummings' family and Downing Street have both previously declined to comment on the backdated council tax bill.