The television commercial watchdog is carefully studying whether to remove an ad that encourages married couples to cheat on their loved ones after 50 complaints were filed against it.

On Sunday night during Underbelly, the Nine Network aired the ad for AshleyMadison, a web-based dating agency made for people who want to have extra-marital affairs.

In the ad, a lingerie-clad woman and a man jumps onto a bed and fondle each other as they are about to get it on.

As they kiss, a message appears on the screen that says "This couple is married."

It is followed by another, "But not to each other."

A last message saying "Life is short. Have an affair." appears above the AshleyMadison website.

According to a spokeswoman from the Advertising Standards Bureau (ASB), some fifty complaints have been made and the ASB board will look into the ad to see if it violated any codes.

"From that there'll be either two outcomes: the complaints will be dismissed or they'll be upheld, which means the ad needs to be modified or removed," she said.

However, the ASB could only make a ruling based on what is in the ad and not what it is about.

A spokeswoman from the Nine Network said that the ad was approved by the classification division of industry body Free TV Australia.

"The business is operating legally and it's an ad that was approved, ... the ad was put to air in the appropriate timeslot," she said.

Relationship psychologist Sarah Gibson said that the viewers disliked the ad possibly because it imposed a threat to the sacredness of marriage.

"There's an argument that this kind of response is a little bit of a puritanical hangover that we carry within ourselves," Gibson said.

"We have this idealised view of marriage, it's the cornerstone of families and the fact a good marriage is good for has been ingrained in our brains.

"It's understandable the ad is a little bit confronting because [for some] infidelity is a negative thing to promote."