The Reform UK leader, Nigel Farage, has been urged to “come clean” over his election campaign in Clacton after a former aide claimed his party breached spending rules.

Farage’s campaign has been accused of falsely reporting his election expenses during his successful run to become an MP last year.

Richard Everett, a former Reform UK councillor and member of Farage’s campaign team, is said to have submitted documents to Scotland Yard showing the party spent more than the £20,660 limit in the Essex constituency.

The news comes as Farage faces increasing pressure to apologise over the racism described to the Guardian by 28 of his peers at Dulwich college.

The latest to speak publicly is Yinka Bankole, who claims to claims that a teenage Farage told him “that’s the way back to Africa”, and said he had felt compelled to speak out after the Reform leader’s attempt at “denying or dismissing” the hurt of his alleged targets. Farage has told reporters that he had never been racist or antisemitic with “malice”.

Reform has strongly denied breaking the law on election spending, and accused Everett of being a “disgruntled former councillor” who was expelled from the party several months ago.

But Labour and the Conservatives said Farage had questions to answer over the allegations.

According to the Daily Telegraph, Everett has claimed Reform failed to declare spending on leaflets, banners, utility bills and the refurbishment of a bar in its Clacton campaign office.

He alleges the party’s official returns report that it came just £400 under the spending limit set by electoral law, and the undeclared spending would have put it above the cap. But he also said he thought Farage himself had been “blissfully unaware”.

The Labour chair, Anna Turley, said: “Nigel Farage needs to urgently answer serious questions about whether he broke the law and misled the public when standing for election to parliament. Our parliamentary democracy relies on people playing by the rules so all candidates have a fair hearing with the public.

“Nigel Farage must come clean and put all the evidence on the table to prove he hasn’t undermined our democracy by breaking the rules. Failure to do so will raise even more questions about what he has to hide.”

The Conservative chair, Kevin Hollinrake, called on the police and the Electoral Commission to investigate Everett’s claims. “We all have an obligation to play by the rules to ensure that our elections are free and fair.”

Everett, who defected from the Conservatives to Reform last year, has since left the party and now sits as an Independent councillor.

A Reform spokesperson said: “These inaccurate claims come from a disgruntled former councillor. The party denies breaking electoral law. We look forward to clearing our name.”