Liz Truss has won the backing of former Tory leadership rival Tom Tugendhat. In a major boost for the foreign secretary’s campaign, Tugendhat wrote in the Times that her plans for vast tax cuts are “founded on true Conservative principles”. The chairman of the foreign affairs select committee also criticised Rishi Sunak’s fiscal policy, saying it is “not right” that the tax burden should be rising when people are heading into winter with “dread”. His endorsement is important as he is popular among Conservative party members and a senior figure in the One Nation group of centrist Tory MPs. It is another blow to Sunak, after the defence secretary, Ben Wallace, also came out in support of Truss. Earlier Sunak admitted a video of him as a youngster saying he had no working-class friends was “silly”, as he defended holding off on tax cuts and claimed Truss’s plans would fuel an inflation “sugar rush”. The Tory leadership contender, who is trailing in the race to replace Boris Johnson, also insisted, during an interview with Andrew Neil, that he would ensure some asylum seekers were removed to Rwanda, even if it was only several hundred as thousands more would be deterred. Sunak faced a tough grilling from the Channel 4’presenter in the interview on Friday night that was dodged by his rival Asked by Neil if there was “not something unsavoury about the son of successful middle-class migrants prepared to turn away asylum seekers with a valid claim”, he replied defiantly: “No.” Though Sunak admitted only several hundred migrants may be removed under the plan that will cost millions, he said many thousands would be deterred from trying to cross the Channel to claim asylum in the UK. Among the questions put to him was whether he was embarrassed by a clip aired on the BBC when Sunak was in his early 20s. It showed the now-Tory leadership contender being interviewed as part of a programme on class. “I have friends who are aristocrats, I have friends who are upper class, I have friends who are working class – well, not working class,” said Sunak in the 2001 clip. The footage was latched upon in the race to replace Johnson when it re-surfaced several weeks ago, with rivals scornful and suggesting it showed the wealthy Tory MP would not be able to relate to those struggling during the cost of living crisis. Sunak addressed the video when pressed about whether he was out of touch by Neil. “We all say silly things when we’re students,” he admitted. “I grew up working in my mum’s pharmacy, and you don’t end up doing that unless you interact with lots of people. I spent my time making sure we served our community. “My parents worked incredibly hard to provide opportunities for me and that’s ultimately why I want to be prime minister because this country allowed my family to provide a better opportunity and future for me.” Sunak, who several polls of Tory members have found is trailing behind Truss in the leadership contest, was also tackled over his refusal to cut taxes and an alleged “U-turn” over cutting VAT on energy bills. Sunak had argued against the tax cut in question in February when he was chancellor, telling the Commons the policy “would disproportionately benefit wealthier households”. On Friday, he admitted it was a blunt instrument but said it was one of the few levers that politicians could pull quickly. He said the apparent volte-face was “absolutely not” a case of poor judgment initially and claimed Truss’ tax cuts – £30bn to be funded by borrowing – would put “fuel on the fire” of already-spiralling inflation. Sunak said the move would be a “sugar rush” that would also push up interest rates and make worse the economic difficulties many will face this winter. Despite being invited for a similar grilling by Neil, Truss followed the lead of Johnson at the last general election and refused to do so. At the end of Friday’s programme, Neil said: “She declined our invitation. Her choice of course. That invitation still remains open.”