Ethics rules for the London mayor must be strengthened as Boris Johnson may have failed to meet the standard expected of public figures over his failure to declare personal links to the US businesswoman Jennifer Arcuri, an inquiry into the affair has found. An investigation by the Greater London Authority’s oversight committee said Johnson had opened himself up to “a perception of lack of due process and favouritism” over Arcuri’s inclusion on trade missions in an unofficial capacity. The inquiry is the latest in a long-running saga concerning Johnson and his relationship with Arcuri, an American entrepreneur whose startup was given £126,000 in sponsorship money and was allowed on three trade trips with the mayor in 2014 and 2015. Arcuri has signalled that the pair were at one point in a relationship and a previous inquiry found there was some evidence of this. After a lengthy investigation, the committee found that Johnson may have broken the Nolan principles of public life. As such, it said City Hall’s code of conduct needed to spell out that politicians should declare an intimate personal relationship if public money is being given to that person. It also said it was “concerned” that emails showed one of Johnson’s advisers gave Arcuri permission to attend a trade mission in New York in an unofficial capacity, although it also acknowledged that she had gained access and sponsorship partly through her own persistence. The committee said the GLA monitoring officer found that Arcuri may have been in a relationship with Johnson in 2012 and 2013. But the officer also found there was no evidence that Johnson had influenced the decision to award Arcuri’s firm with sponsorship monies or allow her to accompany him on trade trips. Johnson avoided a criminal investigation after the Independent Office for Police Conduct (IOPC) in May 2019 found no evidence that he had influenced the payment of thousands of pounds of public money to her, or secured her participation in foreign trade trips that he led. It did find that he had probably breached the Nolan principles of public life. However, the GLA was not legally permitted to investigate whether the code of conduct was broken, and the oversight committee has now recommended its rulebook should be strengthened. Caroline Pidgeon, the former chair of the oversight committee, who oversaw the report, said: “The circumstances surrounding this investigation were uncomfortable for many members of the committee and we remain concerned about the challenge we faced in accessing relevant information … “While the IOPC investigation into the allegations against Boris Johnson found no evidence of a criminal offence, it did conclude that there was some evidence that Boris Johnson was in an intimate relationship with Jennifer Arcuri during some of the relevant period. “If he was in such a relationship, failing to declare this as a conflict of interest could have constituted a breach of the broader Nolan principles, the ethical standards those working in the public sector are expected to adhere to. “We found the evidence we heard from Jennifer Arcuri both frank and honest.” The committee said the code must be updated to ensure that any mayor or assembly member should be in no doubt that they should declare non-financial interests such as personal relationships with individuals. It also recommended that the city’s promotional company, London and Partners (L&P), should do more to publicise its services and sponsorship cash to ensure equal opportunities to all, not just those with connections to it. Pidgeon added that the GLA code of conduct “has potential gaps and areas where strengthening is needed”, and said there was a case for a yearly review of the code of conduct. She also acknowledged that “significant changes have been made” since 2015 in the process for deciding who goes on trade missions.