Former official Sue Gray broke civil service rules after failing to declare contact with Labour over a job offer, a Cabinet Office inquiry has found.
Ms Gray, who led a probe into lockdown parties in Downing Street, was cleared to work for Labour by Parliament’s appointments adviser last week.
It said she could start as Sir Keir Starmer’s chief of staff in September.
Labour said all rules were followed and branded the inquiry a “political stunt”.
The party said the Cabinet Office had “spent weeks wasting time on this Mickey Mouse nonsense”.”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,” a Labour spokesperson said.
Labour said Ms Gray only had one phone call with Sir Keir before she resigned in March, and the conversation did not relate to any government business.
Civil servants – who develop and implement government policies – are expected to be politically impartial.
In a statement, Cabinet Office minister Jeremy Quin said the government’s inquiry found the code “was prima facie broken as a result of the undeclared contact between Ms Gray and the leader of the opposition”.
Mr Quin said Ms Gray was given the opportunity to make representations but chose not to do so.
However, the Cabinet Office cannot impose any retrospective punishments, as Ms Gray is no longer working for the government.
“The rules and guidance that govern the conduct of civil servants are clear and transparent,” Mr Quin said. “It is deeply unfortunate that events have transpired in this way.”
Ms Gray was thrust into the public spotlight last year when she led an investigation into gatherings in government offices during the Covid-19 pandemic, while Boris Johnson was prime minister.
Her report found staff attended events on multiple occasions while the rest of the UK was in lockdown, and partly blamed the leadership in Downing Street.
Mr Johnson faced calls to resign following the report, which contributed to the Tory disquiet that led to his downfall as prime minister.
Some Tories had expressed anger that Ms Gray was offered a job as the Labour leader’s chief of staff, arguing it undermined the impartiality of her inquiry into lockdown-breaking parties.
Last week, the Advisory Committee on Business Appointments (Acoba) said Ms Gray had to wait until September to start her new role with Labour.
Ms Gray told Acoba she received a call from Sir Keir in October last year, when he raised the idea of her working for Labour in a senior capacity.
The committee said it was “quite normal for individuals to discuss the possibility of new roles before leaving office” but “any potential conflict must be declared”.
The committee said there was no evidence her contact with Labour had impacted her actions in her civil service role or her ability to remain impartial.
However, it said there remained “a potential risk to the perceived impartiality of the civil service that would be exacerbated” if she took up the job immediately on leaving office.
As well as a six-month break, the committee also recommended Ms Gray should not be personally involved in lobbying the government on behalf of the opposition for two years from the date she left the civil service.
With a general election expected next year, Ms Gray will play a key role in helping Labour prepare for government, if it wins power.
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