British Prime Minister Boris Johnson's top aide Dominic Cummings defied calls to resign on Monday over allegations that he broke coronavirus rules and undermined the government's response to the health crisis.

The Brexit campaign strategist told reporters he had acted "reasonably and legally" when he drove across the country with his wife while she was suffering from the virus in early April.

"I don't regret what I did... I think reasonable people may well disagree", he said.

Britain was then recording hundreds of deaths daily and following strict lockdown rules requiring people with even the slightest symptoms to stay at home for at least a week.

"I have not offered to resign. No, I did not consider it," a visibly nervous Cummings said.

"In this very complex situation, I tried to exercise my judgement the best I could. I believe that in all circumstances I behaved reasonably and legally."

Cummings did not apologise for his behaviour but did express regret for not asking Johnson -- himself already hospitalised for COVID-19 -- for permission to travel during the lockdown's most restrictive phase.

"Arguably, this was a mistake and I understand that some will say that I should have spoken to the prime minister before deciding what to do," Cummings said.

His "no regrets" comment was the headline for several major newspapers Tuesday.

"No apology. No regrets," said the right-wing tabloid Daily Mail, asking "So how can he survive?"

- Flouting rules -

The scandal raging around his decision to drive to his parents' house while he and his wife were sick threatens to undermine Johnson in the heat of a health emergency that has claimed nearly 37,000 lives.

Johnson announced on Monday that all shops could reopen on June 15, but it was all but ignored by TV stations and newspapers mesmerised by Cummings -- seen as one of the most powerful civil servants of the modern era -- fighting for his political life.

The 48-year-old was already a lightning rod for many Britons over his role in orchestrating the 2016 Brexit campaign that eventually saw Britain pull out of the European Union after nearly 50 years on January 31.

Politicians of all stripes have been joined by scientific advisers and even some members of the clergy in condemning Cummings for flouting the rules.

"If you give the impression there's one rule for them and one rule for us, you fatally undermine that sense of 'we're all in this together'," scientific adviser Stephen Reicher told ITV.

- 'Not a great sign' -

Johnson attempted to draw a line under the scandal in his second media appearance in two days.

"I can understand why people might ask for resignations," Johnson told reporters. "But I think people will make up their own mind over what Cummings had to say."

The ConservativeHome website published a rolling list of MPs from Johnson's Conservative party who have publicly called for Cummings to be dismissed.

It had 20 names on Monday -- still too few to challenge Johnson's 80-seat majority in parliament but growing by the day.

The Politico website noted that the list's publication "in itself is not a great sign for the prime minister".

- Treating people 'as mugs' -

Cummings is an enigmatic figure with an unconventional dress style and direct approach that has endeared him to a segment of Britons who have developed a distaste for the ruling elite.

His role in spearheading the Brexit campaign was made into a TV film that further fed the mystique surrounding him.

But the timing of the revelations about his travels could hardly be any worse.

Britain is just starting to emerge from its coronavirus lockdown and the government wants everyone to keep observing social distancing rules in the coming months.

Bishop Nick Baines accused Johnson of treating Britons "as mugs".

"The moral question is not for Cummings -- it is for the PM and ministers/MPs who find this behaviour acceptable," the bishop tweeted.

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