Keir Starmer and Angela Rayner have received questionnaires from Durham Constabulary, the Labour Party has said, as the force investigates a gathering in party offices in April last year.
The Labour leader has pledged to resign if issued a fixed penalty notice over the so-called beergate row.
Police are investigating whether the party leader and his deputy broke the law by eating curry in an MP’s office with staff after a day of campaigning for the local elections in April 2021.
Starmer has said the accusation made against him was entirely different from the “industrial rule breaking” taking place in Downing Street.
Boris Johnson has been issued one fine for breaking his own Covid rules, and has rebuffed demands that he step down as prime minister despite pressure following the publication of the Sue Gray report last week.
A Labour Party spokesperson said: “Keir Starmer and Angela Rayner have received questionnaires from Durham Constabulary.”
At the time of the Durham gathering, non-essential retail and outdoor venues including pub gardens were open, but social distancing rules – which included a ban on indoor mixing between households – remained in place.
But Labour has argued that food was consumed between work events, meaning it was within the rules.
Earlier this month, Durham Constabulary announced they had reversed an earlier decision that no offence had been committed, after receiving “significant new information”.
Labour sources are confident they can prove the Durham event was work-related and that those present were taking a break to eat while working late on preparations for the Hartlepool by-election.