Boris Johnson's large second job earnings were criticised at Prime Minister's Questions after Sky News' Westminster Accounts revelations.
He said: "Let's reflect on numbers, and in particular those numbers that were shone a light on by [deputy political editor] Sam Coates of Sky.
"In particular those in relation to the prime minister's favourite potential successor which showed over the course of four months in four speeches, he raked in excess of £1 million.
"Does the prime minister not find it utterly perverse that senior members of the Conservative Party are lining their nest in this way, whilst at the same time seeking to deny working people the opportunity to strike for fair pay."
The Westminster Accounts project by Sky News and Tortoise Media revealed Mr Johnson has earned £1,064,785 from jobs outside his MP or prime minister salary since the beginning of this parliament, which started in December 2019.
He is the third highest earning MP, after Theresa May and Sir Geoffrey Cox, with most of his earnings brought in since he stepped down as PM in September. That number is only expected to rise.
The former leader has received more than £1m since October from just four speeches, with that number expected to increase.
Mr Sunak replied by saying he did not think predecessors needed to be mentioned, but added: "I think it was one of his predecessors that did indeed work for Russia Today, if I'm not mistaken."
He was referring to former SNP leader Alex Salmond, who had a show on Russian state-sponsored TV Russia Today from 2017 until February last year when it was suspended due to the war in Ukraine.
Mr Flynn is not the only one to praise the Westminster Accounts project, with Lord Pickles, chair of parliament's ethics watchdog saying he thought the tool provides transparency for the public.
"I've loved what you've been doing," he said.
"I've played around with the toolkit that you've provided. I would have thought from even the casual observer that you've not demonstrated or attempted to suggest there's something sleazy about this.
"All you've suggested is that there should be a degree of transparency as to why the money is needed."