A series of billboards mocking communion biscuits and arguing it should be fine to flush to Koran down the toilet without fear of violence have been banned because they 'discriminate or vilify'.

Prominent atheist thinker Sam Harris, who famously argued with Ben Affleck about Islam on American television earlier this year, will visit Australia on a speaking tour next year.

But organisers are furious APN Outdoor won't them run the advertisements which feature quotes from Mr Harris. They argue: 'To reject these posters is to censor free speech - pure and simple'.

One advertisement said people should be able to flush all books including the Islamic holy text down the toilet without fear of violent reprisals.

Sam Harris, a well known atheist author, is coming to Australia for a speaking tour - and advertisements for it have been blocked by outdoor advertising agencies

Ben Affleck (left) and Sam Harris (right) had a famous spat on an American talk show earlier this year

One of the more provocative entries from the banned advertising campaign

This proposed billboard mocked Catholic communion wafers

Another jokes Jesus Christ who was 'born of a virgin, cheated death, and rose bodily into the heavens - can now be eaten in the form of a cracker'.

'As an atheist, I am angry that we live in a society in which the plain truth cannot be spoken without offending 90% of the population,' a third said.

Desh Amila, from organisers Think Inc, said their repeated arguments with APN to allow the posters fell on deaf ears.

The company referred Think Inc. to a section of the Australian Association of National Advertisers code of ethics.

The paragraph says advertisements must not 'discriminate against or vilify' based on race, ethnicity or religion.

When the ads were refused, Mr Amila said: 'This is specifically saying about vilification about a person or a group of people - we're not vilifying anyone.'

'We are spruiking intellectual discussion about a very important subject matter.'

A spokeswoman for APN Outdoor would only say they would not run the advertisements as they breach national advertising standards

He said religion is a 'reason for many of the conflicts in the world... If you think these quotes are offensive, just open the Old Testament..'

'There are many things one can be offended that doesn't mean one shouldn't speak about it.'

Mr Harris, who will visit in January has been described as a fierce critic of organised religions, with titles of his books including The End of Faith and Letter to a Christian Nation.

He tweeted: 'It seems that the billboards proposed by my sponsor in Australia have been rejected on the grounds that they offend religious sensibilities. Interesting...'

Janine Wood, a spokeswoman for APN Outdoor, told Daily Mail Australia they would not run the advertisements because they breached the OMA code of ethics.

She declined to comment further.