Labour has dismissed Tory accusations that Sue Gray broke civil service rules when she spoke to Keir Starmer about working for the party as “Mickey Mouse nonsense”.
Gray - who conducted the investigation into partygate - quit her senior civil service job in March.
She has been cleared by the official appointments watchdog Acoba to begin her new job as Starmer’s chief of staff in September.
But on Monday the government said Gray had breached guidelines by having “undeclared contact” with the Labour leader while she was still an official.
Cabinet Office minister Jeremy Quinn told parliament Gray should have informed ministers or the civil service when she first spoke to Starmer in October last year, four months before she resigned.
But a Labour Party spokesperson said: “All rules were complied with. The Acoba process makes that clear.
“This statement is a political stunt by a Tory government out of ideas and out of road.
“It says everything you need to know about the Tories that they have spent weeks wasting time on this Mickey Mouse nonsense, while refusing to investigate the serious allegations of sexual assault against their London mayoral hopeful, Daniel Korski.
They added: “We’re looking forward to Sue Gray joining us this September as we continue to show the country that only Labour can build a better Britain.”
Acoba - which is chaired by former Tory cabinet minister Eric Pickles- said there was “no evidence” Gray had done anything to favour Labour while she was a civil servant.
Gray’s appointment by Starmer proved controversial among Tory MPs given that she led the official probe into Boris Johnson and rule-breaking during lockdown.
The former prime minister and his allies complained it showed she was biased against him at the time, even though she compiled her report before any contact with Labour.
Bob Kerslake, the former head of the civil service who died on Saturday, dismissed Johnson’s criticism of Gray at the time as “patently absurd”.
Gray’s report in May 2022 proved to be a bombshell. It detailed events at which officials drank so much they were sick, sang karaoke, became involved in altercations and abused security and cleaning staff at a time when millions of people across the country were unable to see friends and family.
Quinn said today. “This process, led by the civil service, found that the civil service code was prima facie broken as a result of the undeclared contact between Ms Gray and the Leader of the Opposition.
“The guidance on the Declaration and Management of Interests for Civil Servants, which is enshrined in departmental HR policies, sets out that individuals must declare all relevant outside interests to their line manager as soon as they arise.”