Russell Brand has taken aim at the world's leaders, describing Australian Prime Minister Tony Abbott as "one of the worst".

During a sit down interview to mark the release of his new book, Revolution, Brand told Nine's Amelia Ballinger he is "pretty sure he (Tony Abbott) is a lunatic".

"I am pretty sure he is an absolute raving lunatic and the people across Australia are unhappy," he said.

Prime Minister Tony Abbott has been labelled a "raving lunatic" by entertainer turned author, Russell Brand. (AAP) (AAP)

But despite his harsh criticism, Brand had to be reminded who the prime minister of Australia was.

"Who's your one who's in charge of you now?" he asked Ballinger before launching into the criticism.

In Revolution, Brand challenges world politics, in particular, global capitalism, and comes to the conclusion that "the system isn't working".

Russell Brand has criticised global politics and world leaders in his new book, Revolution. (AAP)

"Our governments are corrupt and the opposing parties pointlessly similar. Our culture is filled with vacuity and pap, and we are told there's nothing we can do," he said.

Brand, 39, said his vision is for a "fairer, sexier society that's fun and inclusive.

"This is not a new idea but I hope I've written it in a funny way that's a right laugh with some good swear words," he said.

Revolution made half a million dollars profit in the first eleven days on sale.