Keir Starmer is being investigated by parliament’s standards commissioner over alleged breaches of the rules on declaring financial interests worth more than £18,000. The inquiry was opened last week, and relates to claims about late declaration of earnings and gifts, benefits or hospitality from UK sources. Starmer insisted on Monday morning he was confident he had not broken the MPs’ code of conduct, saying: “There’s no problem here.” During a campaign visit to Wakefield before the byelection on 23 June, the Labour leader told broadcasters that the allegations were not a surprise, adding: “My office is dealing with it and will be replying in due course.” Asked if he was sure he had done nothing wrong, he insisted: “Absolutely confident. There’s no problem here.” Starmer’s spokesperson said he had “apologised for the fact that administrative errors in his office have led to a small number of late declarations” and would provide further information to the standards commissioner, Kathryn Stone. Stone provides very limited details about MPs under investigation, of whom there are currently three: Starmer, the Home Office minister Chris Philp and a Conservative backbencher, Andrew Bridgen. The late declarations by Starmer were understood to relate to hospitality, including football tickets, and book payments. It was revealed last month that Starmer is writing a book about Britain under a Labour government – inspired by notes he started writing during lockdown. He was paid an £18,000 advance by the publisher HarperCollins, which he has pledged to donate to charity. The latest register of MPs’ interests show several entries were added recently by Starmer: the book fee for one to five hours’ work a week since March 2020 received in April, and tickets for two football matches worth more than £2,000 received in March and April. Stone often does not uphold allegations against MPs – dismissing 10 of those referred to her for investigation in the last parliamentary session. Labour sources played down any suggestion Starmer was seeking to hide the payments and hospitality received. Some suspected the allegation had been made to embarrass Starmer at a time when his leadership is already under pressure over being investigated by police for allegedly having a beer with colleagues in defiance of Covid rules. Starmer’s allies have branded him “Mr Rules” in recent months in an attempt to contrast his record as a former lawyer who isolated repeatedly during the pandemic when he and family members tested positive for Covid with Boris Johnson’s. The contrast was used to paint Starmer as a diligent rule-follower and Johnson as a serial rule-breaker, given that the prime minister’s repeated denials that no parties were held in Downing Street during lockdown have been proven to be untrue.