Campaigners in Australia have urged their compatriots to register themselves as Christian in an upcoming national census so that the country is not "officially declared as Muslim".

Many ultra-Christian commentators have said the "no religion" option on Australia's next census could allow Islam to appear more popular than other religions - despite the last census showing more people identified as Buddhist than Muslim.

And since government funding is allocated in part according to census data, one email is reportedly telling Australians who were brought up as Christians to claim they still are when the survey takes place on 9 August.

The debate on social media over Australia’s identity was sparked by the Australian Atheist Federation, which won a campaign to have “No Religion” moved to the top of the census’s religion question.

Religious campaigners said ticking the “no religion” box – which is not meant to be identical with atheism – could result in far fewer people identifying as Christian than usual.

One Facebook user, Norma Henderson, posted: “I implore all my friends… Even if you are not a practising Christian or don’t attend church, please tick Christian if you were baptised.

“Don’t leave the door open to Islam.”

Loading....

An email has been circulating from an unknown source which asks Australians not to tick “no religion”, in an effort to outnumber Islam's followers, Christian ethics group Salt Shakers told news.com.au. A spokesperson for Salt Shakers said the group had told its members to delete the email and not pass it on.

“Bear in mind that although many Australians have no religion these days, the Muslim population in Australia will all declare that they are Muslim and this fact will be counted to ascertain what type of country we are in regard to religion,” says the email.

“Even though you may now have no religion, please consider entering the religion you were christened or born into, when answering this question.

“Otherwise in time Australia will officially be declared to be a Muslim country – because the Australian Bureau of Statistics Census will reflect this.”

Some believe the campaign is also being driven in part by racists and Islamophobes.

The census has already proven controversial following the surprising numbers of Australians who register their religion as "Jedi".

Research has previously shown that moving the "no religion" option to the top of the list increases the number of people who choose it as an option. Both religious and atheist groups have urged people to answer honestly because of issues surrounding funding. It is the only census question which is not compulsory to answer.

Atheists have also pointed out churches in Australia currently pay no tax and do not have to report on their activities in ways other charitable organisations have to.