Boris Johnson would have faced a 90-day suspension if he was still a Member of Parliament, after an inquiry found he deliberately misled Parliament over lockdown parties.
In a damning report, the Privileges Committee said the former PM had committed repeated offences with his Partygate denials.
The suspension would have potentially triggered a by-election to replace him, had Mr Johnson not already stood down last week after seeing the findings.
He called their conclusions “deranged”.
In a blistering statement, he branded the committee a “kangaroo court” and claimed its year-long inquiry had delivered “what is intended to be the final knife-thrust in a protracted political assassination”.
Mr Johnson – who helped the Conservative Party win a landslide election victory under his leadership only three years ago – is the first former prime minister to have been found to have deliberately misled Parliament.
It has been confirmed a by-election to replace him in his Uxbridge and South Ruislip constituency will take place on 20 July.