Canada’s prime minister, Mark Carney, has said the inadvertent leak of classified military plans by senior US officials means that allied nations must increasingly “look out for ourselves” as trust frays with a once-close ally. Speaking a day after it was revealed that a journalist was accidentally included in a group chat discussing airstrikes against Yemeni rebels, Carney said the intelligence blunder was a “serious, serious issue and all lessons must be taken”. He said it would be critical to see “how people react to those mistakes and how they tighten them up”.