The probe into whether Boris Johnson deliberately misled MPs over Partygate faces delays after the Government was accused of being slow to hand over evidence.
The Commons Privileges Committee demanded evidence, including the ex-PMs diaries, WhatsApps, emails and No10 logs more than three months ago for its inquiry into whether Mr Johnson lied about lockdown boozing in Downing Street.
But some of the crucial evidence has still not been handed over, which could hold up the proceedings, sources told The Guardian.
MPs on the seven-strong committee want to summon the first witnesses in the Autumn but no timetable has so far been set out.
It is understood that the schedule is still being finalised but the aim is still to start taking oral evidence before Christmas.
The scandal-hit former PM is expected to be hauled before the cross-party committee, chaired by Labour veteran Harriet Harman, over whether he deliberately misled MPs about Partygate.
Downing Street repeatedly dismissed the Mirror's revelations about lockdown breaking parties, which later led to police fines for Mr Johnson and the new PM Rishi Sunak.
The Metropolitan Police dished out 126 fixed penalty notices to 83 people over 12 pandemic gatherings in Downing Street and Whitehall, including six events Mr Johnson is believed to have attended.
Whitehall enforcer Sue Gray published a damning report on the extent of the boozing, including wine on the walls, vomiting and a brawl, as well as a lack of respect for cleaners and security staff.
The Privileges Committee probe “includes but is not limited to” four statements Mr Johnson made in December 2021 in the Commons, where he denied parties had taken place in No10.
He said “all guidance was followed” - a claim he later corrected, but said he thought was right at the time - and also explicitly denied there had been a bash on November 13 2020.
But the PM was later pictured holding a glass of fizz at a leaving do on that day - which he has since claimed it was his “duty” to attend.
A source said it was “impossible to carry out” interviews before all the evidence had been received, while another said the government was being “f***ing difficult”, the Guardian said.
Misleading Parliament deliberately is a serious matter. Any MP found to have done so can be found in contempt and suspended from the Commons.
A suspension of more than 10 days would automatically trigger a recall petition and potentially lead to a by-election.
Labour's Deputy Leader Angela Rayner said: " Rishi Sunak claims to herald a new age of integrity but is still up to the same old dirty tricks of cover-up and distortion.
"The Government must come clean about the taxpayers’ money wasted on contracting legal advice for Boris Johnson ’s law-breaking."
A spokesperson for the Committee declined to comment.
A spokesperson for Mr Sunak said: “We do continue to take our responsibilities to assist the committee seriously.
"We are in correspondence with them directly and responding to their letters, to their requests. That will continue.”