New Zealanders are rapidly joining HaveAnAffair.co.nz but the new dating website's owners deny members sign up to do as its name suggests.
Almost 500 people have signed up since it was launched last Friday, and it is now receiving almost 6000 page views every day.
People can join for free, but it costs five "credits" to initiate contact with another member. One hundred credits cost $30.
Co-owner Connie Zhou said the website was not about facilitating infidelity.
"We don't encourage people to cheat on their spouses. The site primarily targets those who want to have a short-term, or casual relationship.
"It could be mainly about sex, with no strings attached. And apparently that accounts for a large group of people in New Zealand."
Because of early promotion on a popular Chinese New Zealand website, most of the website's initial members were Chinese.
But Mrs Zhou said they hoped eventual membership would cut across all sections of New Zealand society.
She said while some people would probably use the website to cuckold their spouse or partner, that should be blamed on the relationship and not their website. "If your spouse is already thinking of cheating on you, why do they even need to go on a website? They can do it at their work, in pubs, anywhere is a platform. HaveAnAffair is just another place."
Relationship counsellor Chris Caruana, from website AucklandCounselling.com, criticised the site for encouraging infidelity.
"Affair isn't a word used for single people. Single people hook up, single people get it together, single people have liaisons. But married people have affairs.
"It's a soft inviting term to legitimise people who aren't satisfied with the confines of their relationship, to legitimise having sex outside of that relationship."
Mr Caruana said everyday he saw the hurt and damage affairs had caused to people, which violated what "was at the core of what is deemed to be sacred in a relationship".
While people often justified their cheating, ultimately it was destructive and many relationships could not survive it, he said.
But Mrs Zhou was unapologetic about the website's name.
"An affair means a relationship between two lovers. It could be a short-term or long-term love relationship, and doesn't necessarily mean an adultery."