Former British Prime Minister Boris Johnson said on Wednesday he was deeply sorry for the loss of life during the COVID-19 pandemic as he appeared as a witness at the official inquiry into Britain's handling of the pandemic.

Johnson said at the start of the hearing how glad he was to give evidence and how sorry he was for the suffering of victims and their families.

The hearing was disrupted by a protester, who was asked to leave by the inquiry's chairwoman.

"Can I say that I understand the feelings of the victims and their families, and I am deeply sorry for the pain and the loss and the suffering of those victims and their families," Johnson said.

Johnson, prime minister for three years between 2019 and 2022, resigned in disgrace after a series of scandals including reports that he, and other officials, had been present at alcohol-fuelled gatherings in Downing Street during 2020 and 2021 when most people in Britain were forced to stay at home.

The inquiry has already heard damaging testimony about Johnson's handling of the crisis, including claims of government incompetence, backstabbing and misogyny, his reluctance to lock down, and how he was confused by the science.

He was said to have asked at one point if blowing a hair-dryer up his nose could kill the virus.

Johnson faces two days of questioning in what are likely to be the most emotionally charged sessions of the official investigation so far into why Britain ended up with one of the world's highest death tolls during the pandemic.

He arrived at the inquiry in the dark, more than three hours before the hearing was due to start, avoiding the families of some of those who died from COVID-19. Families had wanted to confront Johnson over claims that he told colleagues he would prefer to see people die in large numbers than order a second lockdown.

Speaking outside the inquiry, families and lawyers of people who lost their lives during the pandemic criticised Johnson and held up photographs of relatives killed by the virus.

Aamer Anwar, the solicitor representing Scottish bereaved COVID families, said Johnson oversaw "a deadly culture of impunity, incompetence" and treating people like "toxic waste".

The inquiry is examining the government's response to the pandemic, which killed more than 230,000 people in Britain and infected many millions more.