Boris Johnson was under pressure to fire Dominic Cummings after his chief adviser was reported to have breached lockdown rules by travelling 264 miles from London soon after displaying symptoms of Covid-19.
The Guardian and Mirror newspapers reported on Friday evening that the police spoke to Mr Cummings — who lives in London — after he was spotted in Durham seven weeks ago and a member of the public told the authorities.
The government had already ordered the general public to stay at home and not to travel. “You should not be visiting family members who do not live in your home,” the guidance said. “The only exception is if they need help, such as having shopping or medication dropped off.”
A Labour spokesman said that Number 10 needed to provide a “very swift explanation” for the apparent breach of the rules during the worst pandemic for generations. “The British people do not expect there to be one rule for them and another rule for Dominic Cummings.”
Ed Davey, acting leader of the Liberal Democrats, said: “If Dominic Cummings has broken the lockdown guidelines he will have to resign. It’s as simple as that.”
Downing Street did not provide any initial response.
A spokesman for Durham Constabulary said: “On Tuesday, March 31, our officers were made aware of reports that an individual had travelled from London to Durham and was present at an address in the city.”
He said officers made contact with the owners of the address who confirmed that the individual was present and self-isolating in part of the house.
“In line with national policing guidance, officers explained to the family the guidelines around self-isolation and reiterated the appropriate advice around essential travel.”
Mr Cummings, the former architect of the successful Vote Leave campaign in 2016, is a key adviser to Mr Johnson.
But senior Tories expressed dismay at the news on Friday evening, with one minister asking: “How can any government minister, or MP for that matter, ask the public to abide by the rules when the adviser closest to the prime minister so flagrantly ignores them. It’s hard to see how he can stay based on what we know.”
Another senior minister said the adviser had acted “like an idiot”.
Another party figure said: “How can cabinet ministers stand up with a straight face and tell people they need to abide by the rules?”
One Tory source told the BBC that the trip was within the guidelines, adding: “Cummings went to stay with his parents so they could help with childcare while he and his wife were ill … no breach of lockdown.”
Downing Street has previously refused to say where Mr Cummings was staying during the lockdown.
The Guardian reported that Mr Cummings was spotted near the gate of his parents’ home in Durham at around 5.45pm on Sunday 5 April, five days after the complaint was made to the police. This was only one week after he started to self-isolate with symptoms of the virus, and at the same time that Mr Johnson came down with it.
The story is acutely awkward for the prime minister because breaking lockdown rules has already led to resignations for other senior government figures.
Neil Ferguson, the epidemiologist whose modelling led to the lockdown, quit as a member of the Sage scientific advisory group after the Daily Telegraph revealed he had been visited by his girlfriend.
At the time health secretary Matt Hancock said he was “speechless” about Prof Ferguson’s behaviour, saying he had taken the “right decision” to resign.
Separately, Catherine Calderwood, chief medical officer for Scotland, was also forced to resign after visiting her second home twice during the lockdown.
Mary Wakefield, the wife of Mr Cummings, wrote an article last month in the Spectator about the couple coping with the lockdown: “Day in, day out for 10 days he lay doggo.” It did not mention his journey to northern England.