Labor frontbencher Doug Cameron says it's Tony Abbott who's the "wacko" after the prime minister sledged the former Labor government in the Washington Post.
Senator Cameron denies he's embarrassed by Mr Abbott's comments.
"I am more embarrassed to have a prime minister who behaves like that when he goes overseas. If you want to use the adjective wacko then you should look close to the prime minister on this one," he told ABC radio.
He said Mr Abbott just couldn't get out of opposition attack mode.
"If he is the prime minister of this country, he should start behaving like the prime minister of the country and start putting our national interest first," he said.
In the interview with the influential Washington Post, Mr Abbott described the former Labor government as a circus, and scandalously wasteful.
Asked about Labor's national broadband network, he replied: "Welcome to the wonderful, wacko world of the former government."
Some commentators suggested he was breaching the convention that leaders did not vent on domestic politics on the international stage.
Health Minister Peter Dutton defended his leader.
"I don't think any international observer who has keenly watched Australian politics over the last six years would be surprised," he told ABC television.
"The previous government was dysfunctional and was problematic. And that's why the Australian people made a judgment at the last election. We have been able to move on from that now."