A film depicting sex acts between men and donkeys was screened at a Sydney film festival last week after an exemption from classification was granted to the festival by the Classification Board.

The federal government agency responsible for classifying films, the Classification Board, did not ask to view Donkey Love before granting permission for it to screen at the Melbourne Underground Film Festival and Sydney Underground Film Festival.

No film can be publicly screened in Australia without first being rated by the Classification Board, which may refuse a classification if it offends standards of morality and decency.

However, it may permit a festival to screen films that have not been rated.

In contrast, the Classification Board banned L.A. Zombie, which features a zombie character having homosexual sex with dead bodies, from being screened at the Melbourne International Film Festival in 2010.

The director of the Classification Board, Donald McDonald, told The Age he refused to grant the film an exemption from classification to screen at the festival because "the film, if classified, would be classified X18+ or RC and, in this circumstance, the law requires the [Classification Board] director to refuse an exemption".

A director of SUFF, Stefan Popescu, said he was surprised the Classification Board had not asked for more information about Donkey Love or to view it before granting the festival permission to screen it.

"I was almost certain they would ask for that film but they didn't," Popescu said.

Donkey Love, which purports to be a documentary about a tradition of Colombian men having sexual relations with donkeys, won best documentary at the MUFF.

"I was very nervous about awarding it," said Richard Wolstencroft, the director of MUFF.

"It's a controversial film but [jury head] Gene [Gregorits] was very insistent it should win."

One scene in Donkey Love shows the filmmakers laughing as they film a man committing acts of bestiality on the side of a road.

The director of Donkey Love, Daryl Stoneage, said the film had divided audiences but had not been banned overseas.

"You make half the room never want to talk to you again and the other half come up to you and tell you what a pair of balls you must have to make a film like this," he said.

"I think when people actually see the film, they get desensitised to the act pretty fast and are able to watch a funny and informative documentary about a cultural practice that most people don't know anything about."

However, he said the whole film had made him feel uncomfortable.

Stoneage was unapologetic about treating the cultural practice of bestiality, which many people would find abhorrent, and illegal, with humour.

"I'm guessing those same people would have a hard time wrapping their heads around a country full of bestiality," he said.

"It's too bad, there should be more funny documentaries.

"I know I think about that every time I watch the 20th documentary about 9/11 being an inside job or some documentary narrated by Leonardo DiCaprio or Matt Damon telling me what's melting or that I should recycle more."

"If you don't think a country full of people having sex with donkeys is funny then maybe there's something wrong with you."

The film does not have an Australian distributor yet, but Tyler Chandler, from the film's production company, said he would be happy to screen the film at other film festivals.

"We don't have any specific policies on bestiality because it is illegal in Australia," said a spokeswoman for RSPCA Australia, Elise Meakin.

"But from our perspective it is unacceptable in any form."