Keir Starmer has defended serving in Jeremy Corbyn’s shadow cabinet, saying he wanted to help preserve the Labour party and that he “always knew there was going to be a day after”. Speaking in separate interviews hosted by the Sun newspaper that included questions from a watching audience, Rishi Sunak and Starmer underwent at times difficult interrogations, including over migration and the NHS. Both party leaders were quick to dismiss the record of their predecessors. Rishi Sunak said Liz Truss’s economic policy was badly mistaken and claimed that a Starmer-led government would create similar fiscal instability. Starmer meanwhile gave his fullest answer yet as to why he had endorsed Corbyn in the 2019 election when he did not believe in him, and why he did not quit to serve on the backbenches as some colleagues had. “Everybody then took a decision about what they did, how we dealt with this,” he said. “I felt that on issues such as Brexit, which I thought were going to define us for decades to come, leaders are temporary, but political parties are permanent, but it was important to have a voice in the shadow cabinet. “It meant that I could challenge on antisemitism, and it meant that the Labour party never veered from its position on things that are fundamental, like Nato,” he said. The entire Corbyn period was, Starmer said, “very difficult for me and for my party”, but he had to look towards the future. “I knew there would be a day after, where we needed to pick it up, to say to the electorate: ‘In 2019, we got this wrong’, and rebuild – we were all working to that end,” he said. “Everybody knew there was always going to be a day after, when we would have the opportunity for a new party, and to make sure our party was there to face the future.” Sunak sought to argue that Labour would be as damaging to the economy as Truss, as he was challenged about the impact of the short-serving prime minister. Asked if he felt “some responsibility for inflicting Liz Truss on the voters”, Sunak stressed that he had fought Truss for the Conservative leadership and warned against her plans. “I was right then, when I warned about Liz Truss. That’s why all of you can trust me now,” he said. “I have also warned about the damage that Keir Starmer would do to our economy. I was saying something that no one wanted to hear, but I was saying it because I believed it. And I’m telling you again now, it all seems a bit familiar. “If Keir Starmer is your prime minister, the economy is going to suffer and all of you are going to suffer. I don’t want to see that happen.” In another pointed remark, Sunak argued that Labour’s decision to scrap the Rwanda deportation plan for asylum seekers would see a rush in arrivals. “Those illegal migrants will not be on planes to Rwanda,” he said. “They will be out on our streets, putting pressure on public services – and by the way, I can tell you now they are queueing up in Calais, waiting for a Starmer government so they can come here and stay here.” Rishi Sunak stopped off in Chelsea after the debate to deliver a brief stump speech to Tory activists. Greg Hands, a trade minister and former Tory chair who was elected with a 11,000 majority in 2019, is seeking re-election in the west London seat. Sunak told local activists he was “not blind to people’s frustrations with me, with our party”, but said “this election is not a referendum on me”. He said Keir Starmer had “changed his mind on every major position that he has taken, including just the other day U-turning on his U-turning about supporting Jeremy Corbyn” and accused the Labour leader of threatening the security of women with his policy on transgender rights.