Parliament's Committee of Privileges is investigating whether Johnson, who was ousted from Downing Street in September, intentionally or recklessly misled the House of Commons in a series of statements, where he said no rules were broken in the gatherings.

If the committee finds Johnson deliberately misled lawmakers, then he could be suspended. Any suspension longer than 10 days could prompt an election to remove him from his parliamentary seat and end his political career.

The former leader, who considered an audacious bid for a second stint as prime minister last year, launched a lengthy defence at the hearing, saying statements he made to parliament had been done in good faith.

"I'm here to say to you, hand on heart, that I did not lie to the House," said Johnson, who has accused the committee of bias. "When those statements were made, they were made in good faith and on the basis of what I honestly knew and believed at the time."

The so-called partygate scandal contributed to the ultimate downfall of Johnson, after months of reports that he, alongside other senior government figures, had been present at alcohol-fuelled gatherings in Downing Street during 2020 and 2021 when much of the rest of Britain was forced to stay at home.

Johnson was fined by police for attending an event to celebrate his birthday in Downing Street in June 2020, making him the first prime minister found to have broken the law while in office. Some 126 fines were issued over the gatherings.

The outcry and repeated accusations of lying over the parties and allegations that a Conservative lawmaker had drunkenly groped two men eventually prompted the resignations of most of his top team of government ministers, including the current prime minister, Rishi Sunak, who was among those fined.

THANKING STAFF

Harriet Harman, the chair of the committee, said it would consider the evidence Johnson had given and may take further evidence in due course. It is expected to report its findings later in the year.

She stressed the importance of ministers telling the truth, saying this went to the heart of the way Britain's parliamentary system functions.

At the start of the hearing, Johnson was made to swear an oath to tell the truth on a bible before giving his evidence.

He said the inquiry had not found any evidence he deliberately misled parliament and said he was banned by the committee from publishing a "large number of extracts" he relied on in his defence.

Asked about events in May, November, and December 2020 when he was pictured talking to colleagues who were drinking, Johnson said some meetings were "essential" to the functioning of government. He said his presence at events was necessary to thank staff for their hard work.

"People who say that we were partying in lockdown simply do not know what they are talking about," he said, crossly.

He said he was "shocked" to be fined and "amazed" by the number of other fines issued.

"I think what happened basically, was that on a few evenings, events did simply go on for too long and I can't apologise for that enough," he said.

Britain had one of the highest coronavirus death tolls in the world with more than 175,000 deaths by the time Johnson said he would step down as prime minister.

The campaign group COVID-19 Bereaved Families for Justice UK said that Wednesday was "a new low" for Johnson and said it was "painful to watch him pull his usual tricks of deflection, self-pity and blaming everyone but himself".

Johnson accepted he had inadvertently misled parliament but had believed what he had said when he spoke.

"I didn't think that those events were an issue. Nobody had previously raised them with me as being things that I ought to be concerned about," Johnson said. "Call me obtuse or oblivious, but they did not seem to me to be in conflict with the rules."