Rishi Sunak and Liz Truss have ruled out freezing energy prices by claiming it would be an expensive, short-term fix that would fail to solve the underlying problem with soaring energy costs. The Conservative leadership contenders were questioned on whether they would back Labour’s new strategy to fix the domestic energy cap during a leadership hustings at Perth Concert Hall on Tuesday night. Truss, the favourite to win the contest, won applause when she said the best strategy to combat rising prices would be to lift the green levy on bills, greatly increase the UK’s gas production in the North Sea and to reverse the recent rise in national insurance rates. Questioned on whether she should heed a poll in the Times showing two-thirds of Tory voters backed Labour’s plans, she said: “What I worry about is putting a sticking plaster on this to say we will find the money but be in the same situation in six months’ time.” The problem will not go away by then, she said, because Vladimir Putin was unlikely to be defeated in Ukraine that soon. “What’s not right is throwing money at the problem without dealing with the root cause,” she added. Sunak said it was far more prudent to target help at pensioners and those on the lowest incomes. “What I will not do is follow policies that risk increasing inflation – especially if it amounts to borrowing £50bn – and put it on the country’s credit card. That’s not right, it’s not responsible and it’s certainly not Conservative,” he said. However, he again attacked Truss’s dismissal of further direct support for the most vulnerable, since her national insurance plans would have no effect on the poorest. “Millions of people are at risk of being tipped into destitution and that will be moral failure,” he said. Outside the venue, about 150 protesters, including trade union activists, independence campaigners, the Socialist Workers party and community campaigners, angrily demonstrated, some throwing eggs at delegates. In a rare glimpse of unity between the two candidates, Truss indicated she would offer Sunak a senior position in her cabinet if she were elected. She said: “It’s important that we unite the Conservative party. We’re all Conservatives. We all want to beat Nicola Sturgeon, we all want to beat Keir Starmer. I will want to appoint a cabinet with all the best candidates, including Rishi Sunak, if I win this election.” Truss also implied she had begun brokering a deal with the Democratic Unionist party to rejoin Stormont’s power-sharing government with Sinn Féin, but that hinged on reforms to the Northern Ireland protocol which are being opposed by the EU. A Northern Irish delegate said her family were anxious to see Stormont’s government running again. Truss said she had been in talks with the DUP about her Northern Ireland protocol bill, adding: “I expect to see things happening and the executive reforming.” Both contenders won applause from the Tory members present, a large majority of whom said at the start of the event they had not yet voted in the contest, by firmly ruling out supporting a second Scottish independence referendum. Sunak agreed the UK was a union built on “consent and democracy” but added: “It’s quite frankly barmy for politicians to focus on a divisive referendum when we’re in a cost of living crisis.” To loud applause, Truss reminded members she had been to primary school in the Scottish city of Paisley. “To me, we’re not just neighbours, we’re family and I will never ever let our family be split up,” she said. But she moderated her attack on Sturgeon in Exeter two weeks ago, when she claimed the first minister was an “attention-seeker” who needed to be ignored. Truss’s Scottish allies have told her that was unnecessarily antagonistic. “What I’m going to ignore is these constant calls for a referendum,” Truss told delegates in Perth. “I will help Douglas Ross to work in a constructive way to help the people of Scotland.”