Jacob Rees-Mogg has attacked Sue Gray as a “friend of the socialists” in a bizarre rant in the Commons.
The Conservative former cabinet minister also suggested the partygate investigator had been “conniving in secret meetings” with Labour.
The attack was part of a a coordinated effort by backbench Tories after Gray decided to become Labour leader Keir Starmer’s chief of staff.
Some Conservative colleagues have expressed doubts over whether stirring up memories of lockdown rule-breaking is a sound political strategy.
Rees-Mogg told the Commons: “Does this not smash to pieces the idea of an independent civil service, when we know that one of the most senior civil servants in the country was conniving in secret meetings with the party of opposition?
“And does this not undervalue years of advice and reports that she has given? Her views on devolution, which were known constantly to be soft, her report into (former prime minister Boris Johnson) which we now know was done by a friend of the socialists.
“Does this not undermine all her previous work and the idea of an independent civil service?”
As a cabinet minister under Boris Johnson, Rees-Mogg had often fielded questions about the Gray report, and repeatedly claimed Gray’s findings would be independent.
It was the-then prime minister who had actually ordered Gray to carry out the report in the first place.
Cabinet Office minister Jeremy Quin said: “We need to make certain this does not damage the impartiality or the perceptions of impartiality of the civil service as a whole.
“I am deeply worried that the approach made by the Labour Party… may serve to threaten and… put that at risk.”