Billboard adverts for a speaking tour of Australia by atheist campaigner Sam Harris have been banned, leading to protests by promoters arguing that the ban amounts to censorship.

Harris, who clashed with actor Ben Affleck about Islam on American television earlier this year, is famous for his no-holds-barred approach to religion.

One of the ads says: "We are now in the 21st century: all books, including the Koran, should be fair game for flushing down the toilet without fear of violent reprisal."

Another says: "Jesus Christ – who, as it turns out, was born of a virgin, cheated death, and rose bodily into the heavens – can now be eaten in the form of a cracker."

The ads have been banned because they "discriminate or vilify". Hoewver, organisers Think Inc say: "To reject these posters is to censor free speech – pure and simple."

Billboard company APN Outdoor told Daily Mail Australia they would not run the advertisements because they breached the Australian Association of National Advertisers code of ethics.

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

However, ThinkInc spokesman Desh Amila said: "This is specifically saying about vilification about a person or a group of people – we're not vilifying anyone."

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