The appointment of Nigel Boardman had already sparked allegations of “cronyism” because he is a non-executive director of the business department – and his father was a Tory minister.
The high-flying lawyer also opposed David Cameron’s limited curbs to lobbying practices a decade ago, and is an adviser to the law firm Slaughter and May, which has received £7m of government contracts.
Now documents from the 1986 London borough elections show Mr Boardman stood to be a Conservative councillor in Islington, north London, where he lived at the time.
He trailed home ninth out of 10 candidates, The Guardian reported, but was an “active member” of the local party, a former associate told the paper.
Labour has called for the inquiry – which is believed to have been completed and handed to the government – to be abandoned altogether.
“After stuffing non-executive director posts with political acolytes, it appears the prime minister is now appointing Tory cronies to lead investigations too,” said Angela Rayner, the party’s deputy leader.
“This investigation is clearly independent in name only and needs to be scrapped in favour of a properly independent investigation that will get to the bottom of what has been going on at the heart of government.”
The controversy comes amid allegations that Jeremy Heywood, the late cabinet secretary, is being set up as the fall guy by the inquiry, instead of a focus on how cabinet ministers responded to Mr Cameron’s lobbying.
The former prime minister bombarded his former colleagues with requests on behalf of Greensill Capital, a collapsed finance firm which employed him.
Rishi Sunak replied to text messages to say he had “pushed” civil servants to explore how Greensill could be included within the emergency Covid-19 loan scheme.
And Matt Hancock, the former health secretary, discussed a proposed payment scheme with Mr Cameron and Mr Greensill – which was subsequently introduced by the NHS.
Dave Penman, the general secretary of the senior civil servants’ union the FDA, has warned against scapegoating and urged the inquiry to accept submissions on behalf of Lord Heywood’s widow.
“The Nigel Boardman inquiry was set up to understand the origins of a scandal that ended with a former prime minister pleading for taxpayer cash for his employer,” he said.
“Fingers were very quickly being pointed at the civil service to distract from the inconvenient truth that David Cameron sought, and was granted, privileged access to cabinet ministers.”
A Cabinet Office spokesperson said: “This is an independent review. Nigel Boardman is a distinguished legal expert, having undertaken a number of reviews scrutinising the government, and he was asked to lead this review following the appropriate due diligence checks.”