Former British Prime Minister Boris Johnson deliberately misled Parliament about the lockdown-flouting parties that undermined his credibility and contributed to his downfall, a committee of lawmakers said on Thursday after a year-long investigation.

A scathing report from the House of Commons Privileges Committee found that Johnson’s actions and his response to the committee were such a flagrant violation of the rules that they warranted a 90-day suspension from Parliament.

While a condemning indictment of the former prime minister’s conduct, the recommendation is largely symbolic because Johnson angrily quit as a lawmaker on Friday after the committee informed him of its conclusions.

The report says Johnson committed “repeated contempts” of Parliament by deliberately misleading MPs with his partygate denials before being complicit in a campaign of abuse and intimidation, the cross-party investigation found.

The Privileges Committee consequently recommended a 90-day suspension, which would have paved the way for a by-election for the former prime minister if he had not quit the Commons in anticipation. However, his resignation means he will escape that punishment, the committee recommended that he should not receive the pass granting access to Parliament which is normally given to former MPs.

Johnson, 58, described the committee as a “kangaroo court” that conducted a “witch hunt” to drive him out of Parliament. A majority of the panel’s seven members come from Johnson’s Conservative Party.

“The committee now says that I deliberately misled the House, and at the moment I spoke I was consciously concealing from the House my knowledge of illicit events,” Johnson said in a heated statement released in response. “This is rubbish. It is a lie. In order to reach this deranged conclusion, the committee is obliged to say a series of things that are patently absurd, or contradicted by the facts.”

He called the committee led by Labour veteran Harriet Harman “beneath contempt” and claimed its 14-month investigation had delivered “what is intended to be the final knife-thrust in a protracted political assassination”.

The report is just the latest episode in the “partygate” scandal that has distracted lawmakers since local news organisations revealed that members of Johnson’s staff held a series of parties in 2020 and 2021 when such gatherings were prohibited by pandemic restrictions. The full House of Commons will now debate the committee’s report and decide whether it concurs with the panel’s findings and recommended sanctions.

The committee also said Johnson should not be granted a pass to Parliament’s grounds.

• A Tell / AP report