A New Zealand judge has dismissed charges against a man who posted semi-naked pictures of his wife on Facebook.

The landmark case tested the new Harmful Digital Communications Act, and it's feared it has set a precedent for future cases.

The husband and wife, who remain anonymous for legal reasons, were separated when the defendant uploaded two photographs of his wife in her underwear onto Facebook.

The Manukau District Court heard how the photos caused her to be angry, anxious and very upset. She remembers feeling unfit for work although she didn't take any time off.

However the judge decided there wasn't enough evidence to prove she had suffered harm and the case was dismissed.

Martin Cocker from Netsafe said this sort of behaviour was exactly what the act was brought in to combat - using technology to harass and intimidate others.

The Harmful Digital Communications Act was made law mid-way through last year and has had successful prosecutions, but Mr Cocker says this case could now set the example.

"It's going to make it harder for people to prove they've been harmed and make it harder to successfully prosecute a criminal case" he told Newshub.

"The judge has said the police didn't prove serious emotional stress of harm and it's going to be difficult to prove that on a case by case basis."

The judge said more detailed and specific evidence from the defendant as to her reaction and feelings to the photos were needed.

Netsafe says it has seen a big increase in complaints of this nature - a few hundred since November last year alone - and it's a growing issue.

Newshub.