Nigel Farage is facing mounting pressure to respond publicly to allegations that his Reform UK campaign in Clacton breached election spending rules, after the Electoral Commission confirmed it is assessing a complaint submitted by Labour.

The Labour party chair, Anna Turley, called on Farage to “urgently come out of hiding” and explain whether his campaign exceeded the legal spending limit, after a whistleblower alleged the party failed to declare thousands of pounds of expenditure linked to the 2024 general election contest.

In a letter responding to Labour, the Electoral Commission said it was “considering your letter and assessing other information in accordance with our enforcement policy to determine if there are any potential failures to comply with the Political Parties, Elections and Referendums Act 2000”.

The commission’s assessment runs alongside a separate police process. Essex Police said it is currently assessing allegations of misreported election spending after a referral from the Metropolitan Police, which received an online report earlier this month.

The claims centre on Farage’s successful bid to become MP for Clacton. Labour has alleged Reform UK may have overspent by around £9,000 above the constituency spending limit, which was £20,660 for the seat at the 2024 general election.

The allegations were made publicly by Richard Everett, a former Reform councillor and a member of Farage’s campaign team, who has since left the party and now sits as an independent. Everett told the Daily Telegraph that Reform’s official election return in Clacton came in about £400 below the legal cap, but that additional costs were not declared and would have pushed the campaign over the permitted total.

Among the costs Everett alleges were not included are spending on leaflets and banners, utility bills and the refurbishment of a bar in the campaign office in Clacton.

Turley said the claims raised questions not only about candidate spending in Clacton but also about Reform UK’s wider reporting of election costs. In her letter to the commission, she said: “If expenditure that ought to have been declared in Mr Farage’s return in Clacton has been included in Reform’s national spending return, or elements of national party expenditure have not been declared at all, there is a real risk that Reform’s party spending return is inaccurate or incomplete, which is a matter for the Electoral Commission.”

Reform UK has denied any breach of electoral law. A party spokesperson said: “The party denies breaking electoral law. We look forward to clearing our name.” The spokesperson described Everett as a “disgruntled former councillor”.

Turley described the allegations as “incredibly serious” and accused Farage of “treating the British people with contempt by staying silent”. She called on the Reform leader to address the claims directly, as scrutiny intensifies over whether the party accurately reported its campaign expenditure.

The Metropolitan Police previously said it had received an online report on Friday 5 December relating to “alleged misreported expenditure by a candidate in connection with the 2024 general election”. Later the same day, Essex Police said it was assessing a report “relating to alleged misreported expenditure by a political party in connection with the 2024 general election, following a referral to us by the Met police”.

Neither force named the candidate or party involved in their public statements, but the Met said the transfer to Essex was due to “the location of the alleged offences”.

Under electoral law, candidates and parties must submit accurate spending returns for regulated periods, with separate limits and reporting requirements applying to candidate and national party expenditure. Potential outcomes can range from regulatory action by the Electoral Commission to criminal investigations where police suspect offences may have been committed, including the submission of false or misleading declarations.

At this stage, the Electoral Commission has not announced a formal investigation, saying it is assessing information under its enforcement policy. Police have also not said whether a criminal inquiry will be opened, stating only that the matter is being assessed.

Farage has not publicly addressed the substance of the allegations in detail. The developments add to political pressure on Reform UK as it seeks to build on its electoral breakthrough, with opponents arguing that compliance with campaign finance rules is central to public trust in elections.