Will Walden, who served as senior counsel to Mr Johnson in 2019, said the former Prime Minister will have realised that the “writing was on the wall” ahead of the release of the committee’s report.
Mr Johnson is “clearly angry and convinced of his own truth,” Mr Walden said, calling his resignation statement “very Trumpian”.
“Boris hates the comparisons with Trump, but it is the language of vendetta. It’s a long rant, and frankly, it’s deeply misleading in places. But it’s very Boris,” he told Sky News.
“He knows a lot of what he’s saying is not true.”
In a blistering attack, Mr Johnson accused the committee of mounting a “political hit job”, accused lawmakers of acting like a “kangaroo court” and said, “a witch hunt is underway to take revenge for Brexit and ultimately to reverse the 2016 referendum result”.
Despite Mr Johnson’s explosive comments, Mr Walden said he “doesn’t recognise that person” compared to the Prime Minister he worked for.
“I think he is a different person. There’s a there’s a bitterness, there’s a pettiness,” he said. “But be in no doubt Johnson is on the warpath. He remains a powerful communicator. He is his own best megaphone.”
Since stepping down as Prime Minister, figures released last month showed Mr Johnson has claimed £2.4million ahead of a speaking tour of the United States, according to the latest register of interest for the MP
The Privileges Committee had been investigating whether Mr Johnson “knowingly or recklessly” lied to MPs when he said that no Covid regulations had been broken by staff in Downing Street during lockdown.
He faced a grilling from the cross-party committee in March which said it will meet on Monday to complete its inquiry.
If the committee had recommended a suspension longer than 10 days, Mr Johnson would have faced a by-election in his seat which he had held with a 7,000 majority.
In a statement, a spokesman for the committee said: “The committee has followed the procedures and the mandate of the House at all times and will continue to do so.
“Mr Johnson has departed from the processes of the House and has impugned the integrity of the House by his statement.
“The committee will meet on Monday to conclude the inquiry and to publish its report promptly.”
In addition, Sir Chris Bryant, the chairman of the Privileges Committee who recused himself from the inquiry into Mr Johnson and was replaced by veteran Labour MP Harriet Harman, said the former Tory leader’s criticisms were “in effect an attack on the whole” of the House of Commons.
Speaking to BBC Radio 4’s Today programme, Sir Chris said: “They may want to conclude that there has been an additional contempt of Parliament by the way that Boris Johnson has behaved in the last 24 hours and in the attacks on the committee, which are in effect an attack on the whole House.
“I don’t think anybody can now be in any doubt that Boris Johnson holds Parliament in contempt.”
