John Bercow should be barred from holding public office or positions of leadership, a former Black Rod has said, as the former Speaker was found to have bullied staff during his tenure in the House of Commons and repeatedly lied to investigators. Lt Gen David Leakey, who made one of the complaints against Bercow and acted as a witness to others, told the Guardian he had been determined to ensure Bercow’s record was examined fully. Leakey said no public institution should give Bercow a position while he refused to show any contrition for his behaviour. Bercow, who joined the Labour party after leaving parliament, was reported to be considering a run for London mayor after Sadiq Khan’s term is over. Labour has since suspended him from the party. He is chancellor of the University of Essex, as well as professor of politics at Royal Holloway. A spokesperson for Bercow said on Tuesday he had “never sought or wanted” to be London mayor. The independent panel that examined parliament’s standards commissioner’s findings concluded that at least 21 complaints against him could be upheld. It banned him from holding a parliamentary pass and said he could have been expelled from the Commons if still an MP. The panel, chaired by the former appeal court judge Sir Stephen Irwin, said: “The findings of the parliamentary commissioner for standards, which we have upheld, show that the respondent has been a serial bully. His evidence in the investigations, the findings of the commissioner, and his submissions to us, show also that the respondent has been a serial liar.” Complainants described Bercow’s “amazing display of temper”, including claims of mimicking, shouting, swearing, public humiliation and smashing a mobile phone while throwing it at a senior staffer. Bercow said the complaints were from staffers who had resisted his modernisation efforts. “To describe what I have experienced as a kangaroo court is grossly insulting to kangaroos,” he said. Leakey said: “People can redeem themselves and I hope John Bercow does redeem himself. But so far as I am aware, he has never ever said one word of contrition to anyone. He never put in place a process to deal with bullying when he had an opportunity to do so. In my view, that disqualifies him from a role anywhere in public life or in any position of leadership or governance. He is uniquely disqualified.” Leakey’s own complaint against Bercow was not upheld and he conceded there were no third party witnesses, but he gave detailed witness testimony of Bercow’s bullying of other staff to the inquiry. “I would never have taken him through the complaints procedure from my own personal point of view because I couldn’t have cared less about his bullying to me personally,” Leakey said. “I had to think very carefully about doing it while I was Black Rod – it would have been written up as the Queen’s representative taking on Bercow.” He said he had been aware of three people – Angus Sinclair, Kate Emms and Lord Lisvane – who had been treated far worse. Multiple complaints by the three were eventually upheld. “I thought that I would make it very public that I was doing it to try and encourage others who had been bullied to do similar because otherwise he and people like him, was simply going to go on getting away with mistreating staff and other colleagues,” he said. Bercow said the process had been unfair, describing it as “feeble conclusions reached [that] would be torn to shreds in any judicial process”. Leakey said the former Speaker could not complain about a system he had helped to enforce. “He will rail about how unfair or unjust it has been. But he was the Speaker in the House of Commons for 11 years,” he said. “He chaired the House of Commons commission. There were endless reports about bullying. If the process that is in place is a defective one in his view now, then he had 11 years of his own failure to put a proper process in place to blame for that.”