The British government failed the public by not having adequate planning in place for the coronavirus pandemic, Prime Minister Boris Johnson's former top adviser and Brexit architect Dominic Cummings told lawmakers on Wednesday.

Cummings, who stepped down in December, apologised for the inadequate response to the crisis when it emerged early last year. Covid-19 has claimed nearly 128,000 lives in Britain, the fifth-highest official death toll in the world.

"The truth is that senior ministers, senior officials, senior advisers like me fell disastrously short of the standards that the public has a right to expect of its government in a crisis like this," Cummings told a parliamentary committee.

"When the public needed us most the government failed," he added. "I would like to say to all the families of those who died unnecessarily how sorry I am for the mistakes that were made and for my own mistakes at that."

Cummings, however, said the British government was not alone in failing to recognise the seriousness of the health crisis and "many, many institutions failed around the world".

"The government itself and Number 10 (Downing Street) was not operating on a war footing in February in any way shape or form," he added.

"Lots of people were literally skiing in the middle of February. It wasn't until the last week of February that there was any sense of urgency."

Cummings' appearance is being closely watched after he launched a series of explosive attacks in recent weeks against Johnson's coronavirus policies and financial dealings.

A divisive figure who carved out a uniquely powerful role during the first 18 months of Johnson's government, Cummings has accused the UK leader of lacking competence and integrity and his government of "appalling ethics".

He previewed his testimony in dozens of social media posts, claiming Johnson had adopted a haphazard approach, initially favouring a so-called herd immunity strategy before belatedly abandoning it when the likely death toll became clear. 

If Britain had had "the right preparations + competent people in charge", it could probably have avoided its first lockdown in March 2020 and "definitely" escaped later ones, Cummings wrote, as part of a 59-message Twitter thread. 

"Given the plan was AWOL/disaster + awful decisions delayed everything, lockdown1 became necessary."

Downing Street has denied ever pursuing a herd immunity strategy.

- Eyesight test -

Cummings, the strategist behind the "Leave" campaign in the 2016 Brexit campaign, was appointed chief adviser by Johnson when he took power in July 2019.

He helped to secure a thumping election victory that December, but his frequent clashes with colleagues are said to have led to persistent tensions and he left government a year later.

The 49-year-old was criticised for undermining the government's lockdown message early in the pandemic when he went on a lengthy cross-country journey with his family.

Cummings claimed he and his wife needed childcare help from relatives after they both developed coronavirus symptoms, and that a lockdown-breaching drive during his stay in the north -- visiting a local landmark -- was to test his eyesight.

Critics labelled his defence farcical, and Johnson and his ministers expended considerable political capital backing him at the time.

Cummings initially kept a low profile after quitting Downing Street last year.

But that changed last month when he used his blog to claim Johnson had sought to use potentially illegal donations to renovate his publicly-funded Downing Street accommodation.

He also made other incendiary claims, including that the Conservative leader had raised the prospect of blocking an internal inquiry into leaks because they could implicate a close friend of Johnson's fiancée Carrie Symonds.

- Sceptical public -

Investigations have been launched into some of the affairs, heaping pressure on Johnson, who nevertheless bought himself political breathing space after a strong showing at recent local elections.

Cummings' evidence could refocus attention on the government's patchy performance responding to the pandemic.

But Johnson's government has also overseen a successful vaccination drive, having offered more than two-thirds of adults at least one dose.

That has coincided with a turnaround in its previously falling ratings.

Meanwhile, the public may view Cummings' critique with scepticism.

A YouGov poll last week found just 14 percent of respondents trusted him to tell the truth, compared to 38 percent who trust Johnson.