Prime Minister Scott Morrison could be excused a little crankiness after his heavy itinerary of jet-setting and world-leader pleasantries.

But it wasn't China, or Labor, or the state of the global economy getting the PM's goat on Thursday, rather a dunny sign in a Canberra office building.

A sign at the restrooms of the DP&C offices in Canberra Credit:Chris Uhlmann/Twitter

Mr Morrison has hit out at a literal sign of the times in the Barton offices of his own Department of Prime Minister and Cabinet, which invites staff to "please use the bathroom that best fits your gender identity".

"You don't need to do this stuff," Mr Morrison told 2GB's Ben Fordham on Thursday afternoon.