The Atheist Foundation of Australia is asking people not to list Jedi as their religion in the country's upcoming census.

Every few years, certain governments ask their citizens to fill in forms about their lives, listing things such as what faith they are, and how many children they have.

Back in 2001, people worldwide thought it would be funny to say they followed the force. It was, but fifteen years on and the joke is striking back.

The AFA has told Newsbeat it's making Australia seem more religious than it actually is, putting atheists at risk of being under represented.

The joke first started in the UK, with a chain email that went around at the turn of the century.

This is how the rumour spread that if enough people in a country listed themselves as Jedi, the government would have to recognise it as an official religion.

390,127 UK citizens took up the cause in the 2001 census - 0.7% of the population.

Interest in the joke in Britain has dwindled quite a lot since then, and by 2011 that number had roughly halved.

Over in Australia, though, it's still going strong. In their latest census 65,000 Aussies still put down Jedi.

That's only 5,000 fewer than 15 years ago. They've still never had as many as the UK though.

There's another census in Australia next week, and the country's Atheist Foundation is worried.

"Unfortunately I think the Jedi joke is a bit old," the group's president Kylie Sturgess tells Newsbeat.

"I've put it down myself in the past, and now we're calling on people to take the census a bit more seriously."

Kylie says putting down a joke religion on an Australian census is the equivalent of spoiling your ballot.

"One thing that we do know about the census is that it's used to decide all sorts of things, from planning education facilities and hospitals, to allocating time slots on public radio and television.

"We're hoping that people who might have put down Jedi, or maybe even their favourite football team, as their religion, to think about what the future of Australia is going to be like, and whether they want to legitimately be part of that."

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