Salty Tories have been accused of pedalling Boris Johnson's "conspiracy theories" in a bitter clash over Labour's appointment of Sue Gray.
Last week the respected senior servant quit her role in the Cabinet Office after being offered a role as Keir Starmer's chief-of-staff.
Labour is beefing up its top team ahead of the next general election - but the Commons heard the appointment could be delayed by up to two years.
Angry Conservatives have lashed out over the appointment, and bitter Mr Johnson jumped on it to claim bias against him when Ms Gray investigated him over Partygate.
Tory Sir Robert Buckland - who brought the matter to the Commons - said he was "surprised and deeply disappointed" by the appointment.
And Cabinet Office minister Jeremy Quin said he has "not been impressed" by the Labour Party over the saga.
Responding to critics, Labour deputy leader Angela Rayner said: "I'd like to thank members of the party opposite for asking why a senior civil servant famed for their integrity and dedication to public service decided to join the party with a real plan for Britain rather than a tired out, washed up, sleaze addicted Tory government."
She continued: "The party opposite is so self-obsessed that they are using Parliamentary time to indulge in the conspiracy theories of the former Prime Ministers and his gang.
"What will they ask for next? A Westminster Hall debate on the moon landings, the bill of dredge in Loch Ness or a public inquiry into whether the earth is flat?"
Mr Quin cast doubt on whether Ms Gray followed the proper process for notifying officials about her decision to take up the post.
He said: "The business appointment rules form part of civil servants' contract of employment. The rules state that approval must be obtained prior to a job offer being announced.
"The Cabinet Office has not as yet been informed that the relevant notification to Acoba has been made."
And Jacob Rees-Mogg, a Boris Johnson loyalist, fumed: "Does this not smash to pieces the idea of an independent civil service when we know that one of the most senior 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's done?"
Labour was urged to reveal when meetings with Ms Gray ahead of the job offer took place.
Labour MP Barry Sheerman said: "The suggestion that the civil service is up in arms is nonsense, this comes from the Prime Minister and his shabby government."
Speaking after Ms Gray's departure was announced last week Mr Johnson - who appointed her to carry out the Partygate probe in the first place - said: ‘So it is surreal to discover that the Committee proposes to rely on evidence culled and orchestrated by Sue Gray, who has just been appointed Chief of Staff to the Leader of the Labour Party."
In a statement last week, a Labour Party spokesman said: “The Labour Party has offered Sue Gray the role of chief of staff to the Leader of the Opposition.
“We understand she hopes to accept the role subject to the normal procedures. Keir Starmer is delighted she is hoping to join our preparations for government and our mission to build a better Britain.”
