A ‘dog act’ isn’t simply ruffling someone’s feathers – it’s an act of betrayal. Caitlin Cassidy explains the meaning of the Australian phrase to Julia Hollingsworth.

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Caitlin, this week Australia’s industry minister, Ed Husic, called US president Donald Trump’s tariffs on aluminium and steel a “dog act”. I grew up in New Zealand, a country so close to Australia and yet so free from the phrase “dog act”. Please tell me – what does it mean, and does it have anything to do with dogs?

Your nation has missed out on a truly scathing critique.