Michael Prescott, a former external editorial adviser, compiled a dossier on issues within BBC News, including failings in the editing of a speech by US President Donald Trump speech, allegations of bias in its coverage of the Israel-Hamas war and transgender issues.
The report, which was leaked, led to the resignations of Director General Tim Davie and head of news Deborah Turness, and a threat by Trump to sue for up to $US5 billion ($A7.7 billion), plunging the public broadcaster into its biggest crisis for decades.
"I do not think it's institutionally biased," Prescott told a committee of MPs on Monday, referring to the BBC.
"Let's be very clear, tonnes of stuff the BBC does is world class, both factual programming and non-factual programming."
He said he thought the political reporting out of Westminster was exemplary but he had written his memo because he believed there were "systemic causes" behind the problems he had found.
He said he had also sent his memo to the Department of Media and the media regulator, Ofcom, because he wanted the corporation to improve the way it dealt with any issues of bias.
"What I was frequently seeing was that the BBC's idea of dealing with something was to change the editors around, tweak the written guidelines but there was never, it seemed to me, any willingness (to look) at exactly what went wrong (with some stories) and whether there were deep implications," he said.
Prescott, a former reporter who became a corporate adviser, was an adviser to the BBC's Editorial Guidelines and Standards Committee, along with Davie and Turness.
Robbie Gibb, a non-executive BBC board member, former BBC journalist and previously Conservative prime minister Theresa May's communications chief, was also a member of the committee.
Some commentators have said Prescott and Gibb worked together to mount an ideological attack on the broadcaster, which they deemed to be too progressive.
Prescott denied the assertion.
"I'm no ideological soul mate of Robbie Gibb," he said.
"I'm a centrist dad."
