LONDON Former British Prime Minister Boris Johnson is stepping down as a member of parliament with immediate effect, triggering a by- election in his marginal seat.

Johnson had been fighting for his political future with a parliamentary inquiry investigating whether he misled the House of Commons when he said all COVID-19 rules were followed.

Parliament's privileges committee had the power to recommend that Johnson be suspended from parliament for more than 10 days if they were to find he did mislead parliament recklessly or deliberately, potentially triggering an election for his seat.

Johnson said he had received a letter from the "privileges committee making it clear - much to my amazement - that they are determined to use the proceedings against me to drive me out of parliament".

"I am being forced out by a tiny handful of people, with no evidence to back up their assertions, and without approval even of Conservative party members let alone the wider electorate," Johnson said in a statement.

"It is very sad to be leaving parliament - at least for now - but above all I am bewildered and appalled that I can be forced out."

Johnson, whose premiership was cut short in part by anger in his own party and across Britain over COVID rule-breaking lockdown parties in his Downing Street office and residence, accused the committee of acting of being the "very definition of a kangaroo court".

"Most members of the committee - especially the chair - had already expressed deeply prejudicial remarks about my guilt before they had even seen the evidence," he said.

"In retrospect it was naive and trusting of me to think that these proceedings could be remotely useful or fair."

Johnson also used his resignation statement to deliver an attack on Prime Minister Rishi Sunak's premiership.

"When I left office last year the government was only a handful of points behind in the polls. That gap has now massively widened," he said.

"Our party needs urgently to recapture its sense of momentum and its belief in what this country can do."

(This story has been refiled to correct a typo in the lede)

(Reporting by Andrew MacAskill, editing by Andy Bruce)