Britain's main opposition party said on Friday that Prime Minister Boris Johnson's top adviser must explain why he apparently broke lockdown rules by travelling to his parents' house more than 250 miles (400 km) from his London home.
The Guardian and Mirror newspapers say Dominic Cummings was seen at the house in northeast England at the end of March and his presence was reported to the police.
A lockdown that began March 23 stipulated that people should remain at their primary residence and not visit relatives.
Durham Police say officers went to a house on March 31 and "explained to the family the guidelines around self-isolation and reiterated the appropriate advice around essential travel."
Police did not mention Cummings by name.
The Labour Party said in a statement that "the British people do not expect there to be one rule for them and another rule for Dominic Cummings."
It said the prime minister's office "needs to provide a very swift explanation for his actions."
Cummings was one of the architects of the successful campaign to take Britain out of the European Union, and later was appointed Johnson's top aide.
He is one of several senior UK officials who have been accused of flouting the lockdown rules that they advocated for the rest of the country.