Rishi Sunak and the Conservatives are refusing to say how many Tories are under investigation for betting on the date of the election, as the row continues to dog their campaign. The prime minister said on Friday he was “angry at the thought that someone might have done the things that are alleged” after three people linked to the Conservatives were made subject to Gambling Commission inquiries, including one from his inner circle. The Conservatives declined to “give a running commentary” on how many more officials, candidates or aides were facing probes, as the prime minister was grilled on the scandal at an event in north Wales. Members of Sunak’s party heckled reporters who asked Sunak about the allegations. Sunak refused to be drawn on whether he was aware of other Conservatives who had placed bets on the date of the election, saying there were “multiple investigations” under way that were independent and confidential. He said: “What I can tell you is, as I said, if anyone is found to have broken the rules, they should not only face the full consequences of the law but I will ensure that they are booted out of the Conservative party too.” The secrecy surrounding the investigations means voters may not know if their candidate is subject to an inquiry before the polls open on 4 July. The scandal has overshadowed the fourth week of the campaign, with Labour maintaining its poll lead of up to 20 points and many constituency-level surveys pointing to a near wipeout for the Conservatives. With anxiety increasing among Tory officials about the scale of the losses, four sources told the Guardian that activists in Yorkshire had been diverted to campaign in the prime minister’s own seat of Richmond, which he last won with a majority of more than 27,000. One source said the regional party had sent a message this week telling activists to stop campaigning in three seats and concentrate on three others, of which Richmond is one. They were then told to focus on Sunak’s constituency. However, Conservatives sources said it was categorically untrue that any extra activists were being sent to the seat to shore up support. When the gambling controversy broke last week, Sunak initially said he was “disappointed” that his close aide, Craig Williams, a parliamentary private secretary, had made a bet on the election date. His mood shifted this week after it emerged that a parliamentary candidate married to a senior Tory campaign official and one of his police protection officers were also facing inquiries. “I am going to say what I said because these are really serious allegations,” he told reporters afterwards on the Conservative campaign bus, as he repeated a line that he was “angry” about the issue. Asked what he was angry at, when he had previously only said he was disappointed, Sunak said: “I was incredibly angry to learn about them when I did learn about them. They are very serious in nature, potentially criminal. The police are involved and that’s why it’s right that they are allowed to do their job without anything compromising the integrity of those investigations.” With Sunak refusing to suspend the candidates or confirm how many more are facing probes, Keir Starmer accused the prime minister of a “total lack of leadership”. On a campaign visit to a window manufacturing company in West Lothian, Starmer said: “The betting scandal reveals everything you need to know about the state of the Tory party, because their instinct when an election was imminent and about to be called was not ‘what’s in the best interest of the country?’ but ‘how do I make some money?’.” He said: “If they were my candidates they’d be gone by now, out of the door. He needs to take tough action. He’s not even saying today whether there are more involved.” Starmer pledged a return to “the politics of service, not self-entitlement” if elected. A Gambling Commission spokesperson said: “Currently the commission is investigating the possibility of offences concerning the date of the election. This is an ongoing investigation and the commission cannot provide any further details at this time.” The commission added: “If someone uses confidential information in order to gain an unfair advantage when betting, this may constitute an offence of cheating under section 42 of the Gambling Act, which is a criminal offence.”