A new documentary about the Femen topless activists shown in Venice has revealed that the feminist group was founded by a man.

The film explores the internal divisions within the Ukrainian group over the guru-like and secretive figure of Victor Svyatski, who is no longer a member.

"Ukraine Is Not a Brothel" by Australia's Kitty Green was screened at the Venice film festival on Wednesday.

Inna Shevchenko, a green-eyed blonde and one of the current leaders of the group, said Svyatski had a "grip" on Femen and forced many women members to quit.

Femen was founded in Ukraine in 2008 and first drew international attention by destroying Ukrainian Orthodox crucifixes. Their main office is in Paris.

Their topless protests on a range of themes from sexism to various forms of discrimination to authoritarianism -- have drawn praise but have also caused deep offence and are sometimes dismissed as lacking true meaning.

Femen have drawn attention worldwide with nude stunts targeting a range of political and religious figures, including Silvio Berlusconi and Vladimir Putin.