Sir Keir Starmer has committed to doing “the right thing and step down” as Labour leader if he is fined by police over an allegation he broke coronavirus laws.

The Opposition leader repeatedly denied breaking the laws in a televised statement on Monday afternoon as he faces pressure over the curry and beer gathering in Durham last year.

He accused the Conservatives accusing him of breaking lockdown rules of “trying to feed cynicism to get the public to believe all politicians are the same”.

“I believe in honour, integrity and the principle that those who make the laws must follow them and I believe that politicians who undermine that principle, undermine trust in politics, undermine our democracy and undermine Britain,” he said, from Labour’s London headquarters.

“I’m absolutely clear that no laws were broken, they were followed at all times, I simply had something to eat while working late in the evening as any politician would do days before an election.

“But if the police decide to issue me with a fixed-penalty notice I would, of course, do the right thing and step down.”

Having faced days of damaging headlines, Sir Keir was attempting to grab the initiative while putting pressure on Boris Johnson over his refusal to resign after being fined by police for a lockdown breach.

Eating during a long day’s work was not against the rules

Questions remained over whether Sir Keir, a former director of public prosecutions, would stand down if Durham Constabulary suggests he may have broken the rules but does not issue a fine, as it did with Dominic Cummings.

Sir Keir first told reporters: “If you’ve made a law you should respect the law and if you’re found to be in breach of it you should step down.”

But pressed further on the scenario, he said: “The penalty for a Covid breach is a fixed-penalty notice, that’s a matter of law, and I’ve set out what the position is in relation to that.”

Angela Rayner issued a statement matching Sir Keir’s commitment and insisting she was at the event “working in my capacity as deputy leader and that no rules were broken”.

“Eating during a long day’s work was not against the rules. We have a Prime Minister who has been found to have broken the rules, lied about it and then been fined. If I were issued with a fine, I would do the decent thing and step down,” she said.

Government minister Chris Philp suggested Sir Keir could be “attempting to pressure the police into clearing him”, describing the move as “deeply inappropriate”.

The Tory MP was responding on Twitter to an ITV reporter saying an ally of the Labour leader said the move “puts some pressure on Durham Police who are being leant on in one direction”.

Sir Keir held talks with advisers on his strategy on Monday, having earlier pulled out of a discussion where he would have faced questions over his intentions.

He also did not attend a memorial service for former MP James Brokenshire at St Margaret’s Church in Westminster, where he was expected join politicians from across the divide including the prime minister and Cabinet members.

The Labour leader had been under growing pressure to set out his position, having called for the resignation of the Prime Minister and Chancellor Rishi Sunak after they were fined for a Covid breach.

A pre-emptive announcement on his future if he too is fined will enable him to continue calling for Mr Johnson to leave Downing Street while he is himself under investigation.

On Friday, Durham Constabulary said they had reversed an earlier decision on the case that no offence had been committed, after receiving “significant new information”.

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

Mr Johnson, his wife Carrie Johnson and the Chancellor received fines for breaking Covid laws in April, along with dozens others working in Whitehall and Downing Street.

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 argues the food was consumed between work events, meaning it was within the rules.

Durham Constabulary ruled that Mr Cummings may have committed a “minor breach” of Covid laws when the then-chief adviser to the Prime Minister infamously visited Barnard Castle in April 2020.

But the force said it would not issue him with a fine in line with its policy not to take “retrospective action” over the rules during the pandemic.

Campaigners from the Covid-19 Bereaved Families for Justice group said Sir Keir’s announcement was the “right decision” that “in contrast to Boris Johnson, shows integrity, decency and respect to the bereaved”.

Some 46% of people believe Sir Keir should resign if he is fined by police, according to a YouGov survey of 1,674 adults over the weekend.

That includes 48% of those who voted Labour at the last election, which is higher than those who voted Tory at 40%.

With the police investigation continuing, 54% said Sir Keir either probably or definitely broke the rules.

Labour MP Mary Foy denied reports that staff were drunk at the event, held in the City of Durham MP’s constituency office.

In a statement, she said: “These allegations about my staff are untrue.

“I have already said that I and my team were working during a very busy period, including facilitating the leader’s visit. I do not believe either I or my office staff broke any rules.”

Durham Constabulary declined to comment further when asked about whether it still has a policy of not issuing retrospective lockdown fines.