In life, we know that infidelity can take a whole range of forms, but what defines an inappropriate relationship when it comes to divorce law.

An inappropriate relationship but might not actually include sexual intercourse but is still something that feels like infidelity to you. It might not be adultery for the divorce petition, either because there is no sex taking place or because you are unable to prove that that sex is taking place.

In life, we know that infidelity can take a whole range of forms. Sexual intercourse with someone other than your husband or wife is obviously infidelity, but so are other forms of sexual intimacy with third parties, as well as emotional unfaithfulness: knowing your partner is on a date with someone else will feel like a big problem even if there’s nothing physically happening.

Only sexual intercourse itself between a man and a woman is adultery in the eyes of the law. (Interesting fact: ‘adultery’ is not available as a legal basis for a divorce in a same-sex marriage.) If you want to file a divorce petition based on adultery, only that kind of sexual intercourse counts. All the other kinds of infidelity are obviously enough to cause someone to want a divorce, but they are not enough for a court to accept a divorce based on adultery.

The simple answer is to base your divorce petition on unreasonable behaviour, but to refer to the inappropriate relationship with another person in one or two of the short paragraphs setting out that unreasonable behaviour. By doing that, you have included within your divorce petition the fact that there is unfaithfulness that has led you to want a divorce, but done so in a way that means you cannot possibly fail to reach the threshold the court requires. We have set out elsewhere examples of particulars that would cover unreasonable behaviour. In this situation, one such reason could be: “The Respondent has, for some months, conducted an inappropriate relationship with another man that has led the Petitioner to feel emotionally abandoned within the marriage”.

This approach is likely to be even more common in same-sex marriages for the reason we set out above.

Take-away fact: if your spouse is sharing themselves physically or emotionally with a third party in a way that you do not accept, that is an inappropriate relationship.