THE Good Law Project will sue the embattled Metropolitan Police over its “failure” to properly investigate partygate, the legal charity has announced.

The organisation, which played a key role in overturning the illegal prorogation of parliament by Boris Johnson to push through Brexit, formally began proceedings against the Met – just one day after the scandal-plagued force was placed under special measures.

Jo Maugham, the director of the project, said: “The Met must explain their seeming lack of action regarding this matter.”

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The Good Law Project accused the force of refusing to answer “legitimate questions” about its investigation into lawbreaking in Downing Street.

Scotland Yard’s belated investigation into the Prime Minister and his colleagues’ rule breaches after the organisation launched similar proceedings against the force in January this year.

The Met has been criticised for failing to issue questionnaires to the Prime Minister about three other lockdown gatherings – in November and December 2021 and January 2022 – despite other attendees being fined over these parties.

One of these cases includes the notorious instance in which Johnson was pictured raising a drink during a party for which he was not fined.

The Good Law Project said its case was necessary because the Met has failed to answer key questions about its partygate investigations and to address “grave concerns about the deferential way in which it is policing those in power compared to how it policed ordinary people during lockdown”.

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Maugham added: “We need the Met to be transparent about its actions and this challenge is grounded in a single, simple idea: for the law to have any meaning, it must apply equally to us all.”

The Good Law Project’s co-claimant is former senior Met office Lord Brian Paddick, who said: “We are determined that the Prime Minister should be held to the same standard as the rest of us."

Scotland Yard has until July 22 to respond to the case.

It comes as the Commons' Privileges Committee opened its investigation into whether Johnson lied to parliament over the scandal with a call for evidence issued on Wedesday.

HM Inspectorate of Constabulary announced it had placed the Met under special measures on Tuesday following a number of high-profile scandals, including the overzealous policing of a vigil in memory of Sarah Everard and reports of racism and misogyny within its ranks.

Wayne Couzens was jailed for life after he was found to have raped and murdered Everard after abducting her in London while still a serving officer with the force in 2021.