A vote will be held later this week on whether a special parliamentary investigation should be launched into Boris Johnson’s Partygate denials. Separate from the Whitehall and police inquiries, this would specifically look at if the prime minister purposely misled parliament. What is the privileges committee? Opposition parties have called for a special body known as the privileges committee to look into if Johnson deliberately misled MPs. The prime minister made repeated denials to the Commons that any rules were broken in Downing Street – but Scotland Yard has now put paid to that, and confirmed that parties which breached lockdown laws did take place in No 10 and other parts of Whitehall. Given that the ministerial code carries the unambiguous direction that any breaches should result in a resignation, Labour wants the matter to be scrutinised instead of being brushed under the carpet. Lindsay Hoyle, the Commons Speaker, has said Keir Starmer, the Labour leader, can table a motion on Wednesday for debate – with a vote on Thursday – about referring the matter to the committee. This cross-party group of seven MPs has a Conservative majority, but is chaired by Labour’s Chris Bryant. It is not convened very often, but is meant to look at possible breaches of privilege or contempt of parliament. How would its investigation work? MPs on the committee would have to look into an incredibly tricky subject – trying to ascertain whether Johnson deliberately misled parliament. This is a charge many opposition MPs admit would be difficult to prove. But to uncover the truth the committee could call for papers, summon witnesses and – if necessary – recommend a sanction such as suspension or expulsion. The sanction would still have to be accepted or rejected by the Commons, so with its large majority the government should expect to comfortably kill off anything that arises. Is there any chance MPs will back a privileges committee inquiry? The short answer is probably not. Partly because many Tory MPs seem to have accepted Johnson’s apology, but also because the Conservative whips’ office may effectively treat it as a confidence vote. This means they could tell any backbenchers that the price for voting with the opposition is being kicked out of the parliamentary party – effectively ending their political career. On Tuesday, when Johnson was quizzed in the Commons if that was the case by the Liberal Democrat leader, Ed Davey, he dodged the question. So what is the point? There are some who feel it is an important constitutional principle that ministers should not be allowed to mislead parliament, so do not want Johnson to get off lightly for fear of setting a precedent. But there are other, more political, motivations at play. There are a large number of Conservative MPs whose backing of Johnson has been far from full-throated, instead choosing to keep quiet, waiting for the Met investigation to conclude and Sue Gray’s report to be published. They will be forced to nail their colours to the mast and vote to let Johnson evade further scrutiny if they decide to oppose a privileges committee investigation. Much wrangling was done over the wording of the motion – the final version of which is yet to be seen – to try to make it as tempting as possible for Tory MPs to back. An initial attempt to have a vote on whether Johnson should be found in contempt of parliament has been abandoned, in favour of a move that is ostensibly more innocuous. It can also be presented as increasing transparency around what has been a very murky issue. Johnson will escape having to defend himself, given he will be on a trip to India. But Labour and the Liberal Democrats are already priming digital adverts to roll out in the run-up to the local elections. They think this could reopen barely healed wounds, allowing them to send the message that Tory MPs are voting to spare their own – Johnson could be saved from further investigation in a manner akin to Owen Paterson.