Police have launched an investigation into allegations that Labour leader Sir Keir Starmer broke Covid-19 rules while drinking beer with colleagues during a coronavirus lockdown.
Durham Constabulary announced the probe on Friday as the opposition leader celebrated his party’s success in the local elections.
The force said it had held off on the announcement to avoid affecting the election.
Following the announcement, Sir Keir, who was celebrating in Carlisle, declined to answer questions about the investigation and left the hotel via a side entrance.
He has dismissed the claims as Tory "mudslinging".
Officers will now examine footage of Sir Keir drinking alcohol with Labour Party employees at a gathering during their campaign for the Hartlepool by-election in April 2021.
At the time of the alleged 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.
Details about the alleged event dubbed "beergate" came to light while Labour MPs were criticising Prime Minster Boris Johnson over the "partygate" scandal.
Sir Keir has dismissed the notion that drinking a beer at the event was comparable to the lockdown-breaking gatherings held at No 10 Downing Street, which resulted in fines for Prime Minister Boris Johnson, Chancellor Rishi Sunak and others.
“Earlier this year, Durham Constabulary carried out an assessment as to whether Covid-19 regulations had been breached at a gathering in Durham city on April 30, 2021," the police said in a statement on Friday.
“At that time, it was concluded that no offence had been established and therefore no further action would be taken.
“Following the receipt of significant new information over recent days, Durham Constabulary has reviewed that position and now, following the conclusion of the pre-election period, we can confirm that an investigation into potential breaches of Covid-19 regulations relating to this gathering is now being conducted.”
Police previously said they did not believe “an offence has been established in relation to the legislation and guidance in place at that time and will therefore take no further action in relation to this matter”.
A Labour Party spokesperson said no rules had been broken.
“We’re obviously happy to answer any questions there are and we remain clear that no rules were broken," it said.
Richard Holden, the Conservative MP for North West Durham, said police were doing “exactly the right thing” in investigating potential lockdown breaches involving Sir Keir.
“It’s vital that the man who wants to be prime minister is held to the same standard as the Prime Minister and everybody else," he said.
When it emerged Mr Johnson was under police investigation, Sir Keir had called it a "mark of shame" and demanded the prime minister resign.
