Boris Johnson's top advisor Dominic Cummings was investigated by police after breaking government lockdown rules, the Mirror reports.
Mr Cummings was seen by witnesses at his parents home in Durham at the end of March, when he was supposedly isolating with coronavirus symptoms at his London home.
The Prime Minister and senior cabinet ministers have repeatedly said that strict rules on movement is essential to slow the spread of the virus and to save lives.
Mr Cummings started suffering from symptoms of coronavirus shortly after Mr Johnson, and was said to be self-isolating with his wife and young son for 14 days.