Prime Minister Kevin Rudd's pristine image is about to be blown away with the release of a new book which claims he is foul-mouthed and launches into expletive-ridden rants in his office when things go wrong.
Author Dr Peter van Onselen says Mr Rudd is more complex than the church-going politician Australians see in public.
He told News Ltd the PM is known for his vile temper, is "somewhat of a potty-mouth" behind closed doors and uses the f-word in private.
Dr van Onselen says there are two Kevin Rudds -- the smooth talking public operator and the private one that only his staff get to see.
The claims are made in the book `Howard's End', which looks at the unravelling of John Howard's coalition government and the rise of Mr Rudd.
Dr van Onselen also co-authored Mr Howard's biography, which was published last year.