David Cameron has condemned Rishi Sunak’s closest parliamentary aide, Craig Williams, for making a “clearly very foolish decision” after he placed a bet on a July election three days before it was called. The Guardian revealed on Wednesday that Williams, who is standing for re-election in Montgomeryshire and Glyndŵr, placed a £100 with Ladbrokes on a July poll. The Gambling Commission has launched an inquiry after the bet was referred by Ladbrokes. On Wednesday night, Williams, the prime minister’s parliamentary private secretary, admitted to the “flutter” and said: “I should have thought how it looks.” The foreign secretary was asked by BBC Breakfast about Williams’s “situation” after the revelation. Lord Cameron said: “His situation, having made this clearly very foolish decision, is that he’s being investigated by the Gambling Commission, and they have considerable powers in terms of what the consequences could be, and I think we have to let that investigation take place. And so I can’t really comment any further on it.” Asked if he was happy for Williams to stand as a Conservative candidate, Cameron said “yes” but then qualified this by pointing out it was too late for the party to remove Williams from ballot papers. He said: “All the nominations are in, and candidates are standing, and I don’t think we can change that. In fact, it’s very important that we don’t make alterations, after these things have been set. But obviously, he’s going to be investigated, and will have to face the consequences of that investigation.” Oliver Lewis, the Reform UK candidate for the seat, called on the Tories to withdraw support for Williams. He told the Daily Telegraph: “This is completely tawdry, low-grade behaviour by somebody who was at the right hand of the prime minister.” The party does have the option of pulling its support as Labour did with Azhar Ali, its candidate in the Rochdale byelection, over comments he made about the 7 October attacks on Israel. Ali’s name was on the ballot paper but without Labour’s official backing he slumped to fourth in a contest that was won by George Galloway. On Wednesday a Conservative party spokesperson said: “We are aware of contact between a Conservative candidate and the Gambling Commission. It is a personal matter for the individual in question. As the Gambling Commission is an independent body, it wouldn’t be proper to comment further, until any process is concluded.” It is understood that a red flag was automatically raised at Ladbrokes as the bet in Williams’s name potentially had been placed by a “politically exposed person”, and the bookmaker is particularly cautious over “novelty” markets. Using confidential information to gain an unfair advantage when betting may constitute a criminal offence. The MPs’ code of conduct also prohibits members from “causing significant damage to the reputation and integrity of the house”. The bet was placed while parliament was still in session. At the last election in 2019, before boundary changes, Williams had a majority of 12,000.