IllicitEncounters.com said 64% of their users identified as Christian in comparison to 6% who said they are atheists.
Claire Page, spokesperson for IllicitEncounters.com said, "It's incredibly ironic that atheists are more faithful than Christians, it proves the argument that what some people perceive as immoral - like adultery - isn't increased by the lack of spiritual guidance."
But Jackie Elton from online dating site Christian Connections disagrees.
Speaking to Premier she said: "There definition of Christian is up the spout because they ask these very generic things, and a lot of people would just say I suppose I'm Church of England, that kind of thing, or I'm a Christian, simple because they don't define themselves as a Muslim."
"Adultery websites spend a lot of time making outrageous claims, everybody's doing it, everybody is committing adultery - so why not do it as well? So they're in the business of creating these sorts of claims just to create publicity."
