British police have said Prime Minister Boris Johnson's top aide Dominic Cummings might have committed a "minor" breach by driving to a scenic spot at the height of the coronavirus lockdown and have closed the politically explosive case.

The Brexit campaign master created a political scandal when newspapers discovered that he left London and took a cross-country trip to stay at his parents' property in early April.

His wife believed at the time she was suffering from the virus and Mr Cummings himself developed symptoms a few days later.

The government orders were for those who suspected they had the virus to stay at home for at least a week, but Mr Cummings claimed that the rules allowed him to leave the house in order to secure childcare for his four-year-old son.

Mr Johnson's most trusted and adviser staged an unusual press conference on Monday in which he made no apologies and blamed the media for misrepresenting his case.

Durham Constabulary has now said it "does not consider that by locating himself at his father's premises, Mr Cummings committed an offence".

However, it added that "there might have been a minor breach" when the family took a drive to a local beauty spot after they had recovered.

Mr Cummings explained that he had blurry vision and decided to test his eyesight by driving to Barnard Castle before returning to London.

The local police department said it had "examined the circumstances surrounding the journey to Barnard Castle ... and have concluded that there might have been a minor breach of the regulations that would have warranted police intervention.

"Durham Constabulary view this as minor because there was no apparent breach of social distancing," it said in a statement.

The Durham police department said it had "no intention to take retrospective action" since this would "amount to treating Mr Cummings differently from other members of the public".

The police findings could still pose a political problem for the British leader.

Several dozen members of his Conservative party have called on Mr Johnson to part with Mr Cummings because the aide's actions threatened to undermine the government's response to the health crisis.

Downing Street said Mr Johnson was not changing his mind and considered the matter closed.

"The prime minister has said he believes Mr Cummings behaved reasonably and legally given all the circumstances and he regards this issue as closed," a Downing Street spokesman said.

Some opposition politicians seized on the police report to redouble their calls for Mr Cummings to either be fired or quit.

Mr Cummings "broke the rules he helped write. Actions have consequences. Your move Prime Minister," Labour party MP Davies-Jones tweeted.

At a press briefing this evening, Mr Johnson denied that the public will fail to heed the coronavirus advice because of the actions of Mr Cummings and again attempted draw a veil over the controversy.

The prime minister said: "No, I don't think that people will respond differently, I think people will listen very carefully to what the messages are."

He added: "I've said quite a lot on this matter already and what I also note is that what Durham police said was that they were going to take no action and that the matter was closed.

"And I intend to draw a line under the matter, as I said yesterday to the Parliamentary Liaison Committee."