British police say Boris Johnson’s senior adviser, Dominic Cummings, breached stringent lockdown rules on a jaunt to a tourist town with his family that has sparked fury across the country.

But Durham police will not take further action against Mr Cummings for the trip.

In late March, Mr Cummings drove 400 kilometres from London to his parents’ home in Durham to self-isolate with his wife and son after his wife developed coronavirus symptoms – despite a government order that people with symptoms should stay home.

The trip was revealed late last week. On Monday Mr Cummings fronted the media in the rose garden at 10 Downing Street. He said he had no regrets about the trip, which he said was to ensure there would be care for his four-year-old son if he and his wife fell ill.

Mr Cummings also made another trip on April 12, driving 40 kilometres from his family’s property to the tourist spot Barnard Castle. He said it was to test his eyesight before returning to London.

Demonstrators near Mr Cummings’ London home make their feelings clear.

Both journeys have sparked fury in Britain, with MPs, church leaders, police officers and scientists saying he has damaged citizens’ trust in public health messaging.

As many as 60 MPs in Mr Johnston’s own Conservative Party have joined calles for Mr Cummings to quit – or be sacked.

A YouGov opinion poll has found a majority of Britons also think Mr Cummings should resign for – in their view – breaking the lockdown rules.

Durham police said the trip to Barnard Castle was a “minor breach” of the regulations that would have warranted police intervention.

“Had a Durham Constabulary police officer stopped Mr Cummings driving to or from Barnard Castle, the officer would have spoken to him, and, having established the facts, likely advised Mr Cummings to return to the address in Durham, providing advice on the dangers of travelling during the pandemic crisis,” the police statement read.

An unrepentant Mr Cummings faces the media at 10 Downing Street. Photo: AAP

The British PM is standing by his senior aide, despite the police findings.

“The police have made clear they are taking no action against Mr Cummings over his self-isolation and that going to Durham did not breach the regulations,” a spokesman for Mr Johnson said.

“The Prime Minister has said he believes Mr Cummings behaved reasonably and legally given all the circumstances, and he regards this issue as closed.”

Hours before the police statement, Mr Johnson had announced that Britain’s coronavirus lockdown will ease next week for most people.

In England, up to six people will be able to meet outside and schools will gradually reopen from Monday, he said.

He stressed that the changes were “small tentative steps forward”, and health experts have warned the situation remains finely balanced with new COVID-19 cases declining, but not very quickly.

Governments in Scotland, Wales and Northern Ireland are responsible for their own public health policy.

-with AAP