Senior Conservatives have launched a bid to stymie Labour’s “unprecedented” hiring of outgoing civil servant Sue Gray, amid claims the rules for departing senior officials had been breached. Conservative MPs demanded the appointment be blocked for up to two years given her “knowledge of the most sensitive details of government ministers”, while Boris Johnson’s allies ramped up their campaign to discredit the Partygate inquiry she ran. Keir Starmer refused several times on Monday to say when he first approached Gray about the role. He insisted they had no contact while she was investigating Partygate and that “nothing improper at all” had happened. The row rallied an abnormally high number of Tories to attend an urgent question in the House of Commons on Monday, which saw warnings about it leaving “a dark stain on democracy” and sparking a “constitutional crisis”. In a bid to pile pressure on Labour, paymaster general Jeremy Quin told Starmer to “come clean” about the details of any meetings held with Gray before she accepted the offer to become his chief of staff last Thursday. Doing so would “dispel concerns” and speed up an internal review by the government of the circumstances leading up to Gray’s resignation last week, he said. Although outgoing senior civil servants are meant to seek advice from the Advisory Committee on Business Appointments (Acoba) before any announcement about their future work is made, Quin said the “relevant notification” had not yet been made. Government sources pointed to a Labour spokesperson confirming last Thursday that she had been offered a job with the party “subject to the normal procedures” as evidence the rules had been breached. In a bid to undermine Labour’s commitment to probity, Quin mocked the party for wanting to toughen up the rules for departing ministers and civil servants. “Why weren’t the current ones followed?” he asked. Labour sources hit back, suggesting details about Gray’s departure from the government and hiring by Starmer had been leaked. “The government attack totally ignores the reality of how this came into the public domain,” said one. “It was always our intention that the Acoba process would run its course before anything was announced.” Angela Rayner, Labour’s deputy leader, accused Tory MPs of “indulging in the conspiracy theories of the former prime minister and his gang”. She said they had debased and demeaned standards in public life and accused the government of “playing games” instead of focusing on “the real issues facing this country”, such as the cost of living crisis. Gray’s hiring drew ire from many Tories, including the former justice secretary Robert Buckland, who said the “fundamental trust” between all ministers and officials was at risk. He raised the prospect of Acoba recommending Gray be blocked from taking up the role for up to three years. Jacob Rees-Mogg said the move had “smashed to pieces” the idea of an independent civil service. Taking aim at the Partygate report she authored, which helped uncover parties held in Downing Street during Covid lockdowns, he said her bid to join Starmer’s team would “undermine all her previous work”. But privately, some Tories fear that any return to the issues around Partygate spells trouble for the party. One said: “Her report contained findings of fact. It is not in dispute there were law-breaking parties and whatever Sue Gray doeswill not alter that.” In a series of leaked WhatsApp messages obtained by Sky News, MPs rowed about the focus of the issue. Jackie Doyle-Price, a former whip and minister, reportedly reminded colleagues that Johnson appointed Gray to lead the Partygate probe. “So much for a stitch up,” she said. “He wasn’t brought down by partygate. Or by Whitehall. He lost the confidence of the parliamentary party … This anti-Whitehall pile on is simply burning our constitution.” Doyle-Price added: “Decades of public service where she has inspired respect on all sides don’t deserve to be trashed by a herd of Conservative MPs who just want to fight a partisan battle. I am quite ashamed of what I see.” Another former minister, Tim Loughton, gave a similar warning. He wrote: “Impugning her integrity about the way she handled Partygate without evidence of what she may have done differently in light of the above only refocusses public attention on Partygate and puts us on the defensive to prove something most of us cannot prove at this stage at least.” But Nadine Dorries, one of Johnson’s staunchest allies, said Gray had undermined “the foundations of our democracy and how we govern”. She wrote: “Who knew about Rishi’s wife financial affairs/non Dom etc? I don’t know if it was her but my understanding is that very few people did know and she was one of them and she knew it all. A lot may suddenly begin to make sense.” An inquiry by the privileges committee into claims Johnson misled parliament about the law-breaking gatherings is nearing its conclusion. The former prime minister is due to be grilled in a televised hearing by the seven-member group of MPs, which has a Tory majority, later this month. After concerns were raised about £220,000 of taxpayers’ money being used to fund Johnson’s legal defence, the Guardian understands the National Audit Office has held “an initial discussion” with the Cabinet Office about the matter. A source close to Johnson said he was confident the committee would vindicate him, and claimed that its interim report last week “offered not a shred of evidence that a contempt had been committed even after nearly a year of work”.