PARTYGATE investigator Sue Gray broke civil service rules “as a result of the undeclared contact” between her and the Labour Party, according to a Whitehall investigation.

The former senior civil servant is due to take up the role as Opposition leader Keir Starmer’s chief of staff after being cleared to start the job in September by the Advisory Committee on Business Appointments (Acoba), the anti-corruption watchdog.

But in a separate Cabinet Office inquiry, it was found that Gray, who refused to give evidence to the Government probe, broke the civil service code due to her contact with Labour ahead of her resignation in March.

The result was briefed ahead of Monday’s announcement, which came in the form of a written ministerial statement.

Labour branded the investigation “Mickey Mouse nonsense” and said the conclusion is a “political stunt by a Tory Government”.

Cabinet Office minister Jeremy Quin said: “I can now confirm that the Cabinet Office process looking into the circumstances leading up to Gray’s resignation has been concluded.

“As part of the process, Gray was given the opportunity to make representations but chose not to do so.

“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 Gray and the Leader of the Opposition.

READ MORE: Partygate investigator Sue Gray given six-month wait for Labour job

“The rules and guidance that govern the conduct of civil servants are clear and transparent. It is deeply unfortunate that events have transpired in this way.”

Acoba on Friday recommended that Gray have a six-month cooling-off period, starting from the day she quit the civil service, before taking up her new role with the Opposition, allowing her to start in two months’ time.

The watchdog ruled it had seen “no evidence” that her decision making or impartiality was “impaired” while serving in Whitehall.

Government figures had lobbied Acoba to impose a waiting period of 12 months after complaints about Gray’s move to join the Labour leader after leading a high-profile investigation into Boris Johnson over lockdown breaches in No 10.

But while Acoba chairman and Conservative peer Lord Pickles said he “shared” some of the concerns raised by departments over the potential risk to the civil service’s integrity due to her job switch, he dismissed the call for a lengthier delay.

Responding to the Whitehall probe conclusion, a Labour Party spokesman 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.

“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.”

The National: Tory mayoral hopeful Daniel Korski has denied allegations he groped a woman in No 10

Korski, a former Downing Street adviser during David Cameron’s tenure, pulled out of the race last week to be the Tory candidate to take on Sadiq Khan in the capital after it was alleged he groped a TV producer in No 10 a decade ago.

The Cabinet Office has ruled out investigating the claims, which Korski “categorically” denies, made by Daisy Goodwin.

Gray is expected to begin the task of preparing Labour for government ahead of a likely general election next year, with Starmer’s outfit well ahead of Rishi Sunak’s Tories in opinion polls.

According to evidence handed to Acoba, Starmer raised the possibility of Gray joining his team when he called her in late October 2022.

She told the committee she was “open to such a possibility” but there was no formal job offer until March 2 – the day she resigned.

The investigation into partygate compiled by Gray, after it was ordered by former prime minister Johnson while he was in No 10, was published last May.

Along with her Covid rule breaches investigation, Gray held a number of senior roles in the civil service, including leading the Cabinet Office’s propriety and ethics team.

Her final role was as second permanent secretary at the Department for Levelling Up, Housing and Communities.