The recent charge stems from a lawsuit, filed under an adultery law adopted into Cambodian legislation in August last year with the support of the ruling party under Hun Sen, Cambodia's prime minister and an adversary of Ranariddh.
Supporters of the law say it helps married couples to live in harmony. But opponents of the legislation say it is unnecessary when Cambodia has other higher priorities to tackle, such as corruption and poverty.
Muth Chantha, a spokesman for Ranariddh, called the adultery charge "politically motivated", saying it was designed to prevent the prince from returning to Cambodia and continuing his political work.
The adultery charge is Ranariddh's latest legal trouble. He was sentenced to 18 months in prison after being sued for embezzlement by members of the Funcinpec party, a party he once led.
Last week, Sao Meach, a municipal court judge, ruled there was insufficient evidence proving the prince had embezzled money from the sale of the Funcinpec party headquarters.
But he said the prince was guilty of intentionally registering the new property, bought with money from the sale of the old headquarters, in his own name instead of Funcinpec's and therefore had breached the trust of the party.
Ranariddh is said to be currently living in France.