Sir Keir Starmer and Angela Rayner have received questionnaires from Durham Constabulary over a potential breach of lockdown rules.
The force is investigating a gathering in party offices in April last year in which the Labour leader was pictured drinking beer and eating curry after a day of campaigning.
Deputy leader Rayner was also at the event, held at a time when people were banned from socialising indoors except with their household or support bubble.
There were some exemptions for work meetings – so a key question for police will be whether this meal at the end of the day was necessary.
If he ends up being fined by police over the meal and drinks, Sir Keir has pledged to resign.
The incident took place at Durham Miners’ Hall during a day of campaigning in the Hartlepool by-election.
Labour has insisted the gathering was a legitimate work meeting and within what was permitted under the law at the time.
But Sir Keir said that if authorities drew a different conclusion, he would ‘do the right thing and step down’ as a ‘matter of principle and honour’.
Meanwhile Boris Johnson is facing more and more calls to quit from his own MPs over his role in the Partygate scandal.
A no confidence vote against the Prime Minister is growing after civil servant Sue Gray published her report on lockdown-busting parties in Downing Street and Whitehall.
Johnson previously paid a fine for breaking Covid rules by attending his own birthday party in June 2020, a time when social gatherings were banned.
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