Outgoing UK PM Keir Starmer and US President Donald Trump (R)US President Donald Trump took aim at outgoing UK Prime Minister Keir Starmer on Monday, saying that the Labour Party leader's policies on energy, immigration and relations with Washington contributed to his downfall.Speaking to reporters during an Oval Office event, Trump struck a friendly tone before launching into a sharp critique of Starmer's record."I think he’s a lovely man," Trump said, before accusing the British leader of squandering the UK's energy potential by failing to fully exploit North Sea oil reserves and allowing "windmills all over the place"."The UK buys much of its energy. You know where? Norway. You know where they get their oil? The North Sea," Trump said. "The UK has a much better portion of the North Sea - they don't want to do it for environmental purposes."Trump, who had earlier predicted Starmer's departure in a Truth Social post, said the Labour leader was "sort of a friend of mine" but suggested he had not done enough to support the United States on key geopolitical issues, including Nato and the conflict involving Iran.One point of contention, Trump revealed, was Britain's initial reluctance to approve the use of RAF Akrotiri, a British military base in Cyprus, for US strikes on Iranian targets. The two leaders reportedly clashed over the issue, with Trump expressing frustration over the delay."He said we can't use the island to land. That was a first," MAGA supremo said, adding that Starmer had eventually relented but that "was a bad move" that "hurt him badly".As Starmer prepares to step down as Labour leader, Trump said the British prime minister's "biggest political vulnerabilities were clear.""I wish him well," Trump said. "But he's got two problems: energy and immigration - and crime. But energy and immigration. He's really hurt himself very, very badly."Starmer announced on Monday that he would resign as Labour leader while remaining prime minister during a managed transition, following months of mounting pressure from within his party and a series of disappointing election results that weakened his authority.Attention is now turning to veteran Labour figure Andy Burnham, the former mayor of Greater Manchester, who is widely viewed as the frontrunner to replace Starmer. If selected, Burnham would become Britain's seventh prime minister in just a decade.