Sue Gray may have broken civil service rules if she failed to tell ministers about her meetings with Labour, as a senior frontbencher could not say when talks first began.

Ms Gray, who investigated partygate, quit her Cabinet Office role last week to become Sir Keir Starmer's chief of staff.

On Sunday morning, Jonathan Ashworth, the shadow work and pensions secretary, was unable to say whether she had made senior Government figures aware of her conversations with his party.

The Directory of Civil Service Guidance states: “As a general principle, there is no objection to contacts between senior civil servants and leading members of the Opposition parties if the latter wish to inform themselves about the factual questions of departmental organisation or to keep abreast of organisational changes.

“Such contacts should always be cleared with departmental ministers.”

Earlier this week, one Government source told The Telegraph that Ms Gray had not declared any meetings with Labour in the past few weeks.

Shadow work and pensions secretary 'not privy to HR decisions'

In an interview with Laura Kuenssberg on Sunday, Mr Ashworth could not answer when asked three times about when conversations started between Ms Gray and his party leader, as he was “not privy to HR decisions”.

“First of all, we know that Keir Starmer has for several weeks now been looking for someone to fill this role,” Mr Ashworth said.

“She was always going to be on the list when we knew there was a vacancy that emerged. She’s quite rightly going to go through a process. There’s proper procedures in place when a senior civil servant leaves the civil service and I’m sure she’ll set it all out when she has those conversations.”

On the prospect of whether Ms Gray had followed the rules, Mr Ashworth repeated he had not been “privy to the conversations” and added the mandarin “will outline all of this in the proper way, which will follow the procedures”.

“You’re asking me to speculate on something when I’ve not been privy to the conversations… You are asking to engage in a hypothetical, if I may say so.”

Asked by Ms Kuenssberg if it would matter if Ms Gray “did not follow the rules to the letter”, Mr Ashworth replied: “I’m confident that Sue Gray is a woman of immense integrity, and she will set all of this out as she follows the proper processes and procedures – as one does when you’re a senior civil servant and you leave the civil service.”

'Just another brick in the wall' in undermining public trust

Earlier this week, The Telegraph revealed Susan Acland-Hood, permanent secretary at the Department for Education, reminded civil servants they “should tell your permanent secretary right away” if they received contact from any shadow cabinet politician.

Labour sources have confirmed to Sky News that Ms Gray’s application to Acoba, the appointments watchdog, will be submitted on Monday, and that she recognised she would have to reveal when talks with Sir Keir Starmer’s party began.

It came as Sir Jake Berry, the former Conservative chairman, warned Ms Gray’s application was “just another brick in the wall” in undermining public trust in Whitehall.

Speaking to Camilla Tominey, The Telegraph’s Associate Editor, on her GB News programme, Sir Jake said: “It’s this appearance of bias, this sort of appearance that Boris Johnson may have been subject to the biggest stitch-up since the Bayeux Tapestry.”

Labour confirmed earlier this week Ms Gray had been offered the job, but refused to say how long Sir Keir had been courting her for the role.

The party admitted they had known each other since its leader was the Director of Public Prosecutions between 2008 and 2013.

Labour sources also pointed to reports Sir Keir wanted his new chief of staff to be more involved in “transition to government planning” than “campaign planning”, and that he had always wanted a senior civil servant to succeed Sam White, who departed in November.

The party denied Ms Gray had been approached “because [Sir Keir] somehow wanted Government gossip”, and insisted she had kept secrets on behalf of a number of different political parties while working in Whitehall.