Filmmaker P.J. Hogan has turned a former nanny into an enemy after documenting her descent into madness in his new film.

The director reteamed with his Muriel's Wedding leading lady Toni Collette for the film Mental, which centres around the unstable woman his father brought home to look after his kids after their mother was committed.

Hogan admits the real-life character, Shaz, exists - and she's not very happy with the way she's portrayed in the movie.

The moviemaker tells, "Shaz entered my life when I was 12 years old. The events depicted in the film are exactly what happened in my life. When I was 12 my mother had a complete nervous breakdown, ended up in a mental hospital. My dad who was a local mayor and up for re-election, said to us, 'Nobody votes for a guy whose wife is crazy so here's the official story - your mum's on holiday. Stick to it.' And we did.

"But then he was stuck with us and we were a wild bunch of kids who must've driven dad to the point of near breakdown. He stopped for a hitchhiker and trusted her because she had a dog. He really didn't like dealing with us... We came home from school and there was this strange woman that he had picked up on the side of the road sitting in our living room, a hunting knife sticking out of her boot, her crazy dog growling at us. She set the dog onto us and made us clean! She whipped us into shape and we ended up loving her.

"She is the first champion I ever had in my life. When she was committed she wanted us to do something crazy and break her out of the hospital but we didn't because we were just kids. She's still out there and on Twitter @ShazIsMental. She dislikes the film immensely and anyone interested in Shaz's side of the story should follow her. She's still, as we say in Australia, mad as a cut snake!"