The former chancellor said: “Liz, we have to be honest. Borrowing your way out of inflation isn’t a plan, it’s a fairy tale.” Ms Truss hit back, saying: “You can’t tax your way to growth”, referring to Mr Sunak’s refusal to reverse the rise of National Insurance. The foreign secretary has argued that debt from the pandemic should be treated as “war debt” and repaid over a longer period of time. Liz Truss campaigners privately admit Rishi Sunak will be in the bottom two, and are now trying to position her as the best candidate to challenge him on the economy. A senior campaign source said: “The next election will be about the cost of living, so we need a prime minister who has a plan, credibility and experience on the economy. Liz has gravitas and vision for the economy and will be ready to lead from day one.” It comes as the Center for Social Justice think tank, founded by Ian Duncan Smith, polled favorably for tax cuts for families after Mrs Truss made it a key part of her campaign last week. His survey, conducted by Opinium, found that more than half of adults agreed with tax reforms to give more support to married couples with children, compared to one in five who did not.