British Labour leader Keir Starmer has insisted he is "confident no rules were broken" after it was announced he is to be investigated by police amid allegations that he broke lockdown rules last year.

Mr Starmer - who has repeatedly called for Boris Johnson to resign over rule-breaking in Downing Street - told reporters: "Obviously I understand the police need to do their job, we need to let them get on with that but I'm confident there was no breach of the rules."

Durham Constabulary announced earlier today it was investigating the claims following receipt of "significant new information", having previously said they did not believe an offence had been established.

The police U-turn follows mounting pressure on the force to re-examine the allegations after footage emerged of the Labour leader drinking a beer with reportedly up to 30 colleagues at a constituency office in Durham in April 2021 during campaigning for the Hartlepool by-election.

Mr Starmer, who is on a victory lap of England following some successes in local council elections, earlier declined to answer questions from reporters in Carlisle this afternoon after police confirmed their change of heart.

A Labour Party spokesman said: "We're obviously happy to answer any questions there are and we remain clear that no rules were broken."

The Labour leader speaks to the media in Barnet, London

A police statement said: "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.

"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 did not elaborate on what the new information involved.

Allegations against Mr Starmer refused to subside in the run-up to the elections, with the Labour leader this week saying he wanted to focus on the cost-of-living crisis and not Conservative "mudslinging".

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 in England.

Mr Starmer has repeatedly denied breaching the rules.

In January, he said the Prime Minister "needs to do the decent thing and resign" after he became embroiled in lockdown breach allegations.

His colleague, Angela Rayner, who was with Mr Starmer at the Durham gathering in April 2021, also questioned Mr Johnson's suitability as Prime Minister.

She wrote on Twitter: "Boris Johnson's Downing Street is under police investigation, how on earth can he think he can stay on as Prime Minister?"

Durham Police previously said their "general approach" was not to take "retrospective action", including against former Downing Street chief adviser Dominic Cummings over his notorious trip to Barnard Castle to "test his eyesight" while England was in lockdown.

The force has now been asked to confirm whether this general approach remains in place.

Mr Starmer previously said no restaurants or pubs were open at the time of the alleged offence, and the hotel he and his colleagues were staying in did not serve food, so "if you didn't get a takeaway then our team wasn't eating that evening".

Conservative MP for North West Durham Richard Holden said the police are doing "exactly the right thing" in investigating potential lockdown breaches involving the Labour leader.

Mr Holden, who had been pressing police to investigate after presenting new evidence, said: "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."

Mr Johnson, his wife Carrie Johnson and Chancellor Rishi Sunak are among those to have already been fined for breaking Covid laws.