A mother who suffered more than a decade of physical and sexual abuse at the hands of her husband has been denied ACC cover because of a technicality.

The Christchurch woman, who cannot be named, married in 1994 and her husband soon began to display abusive behaviour. That escalated into continual sexual, psychological and physical abuse until she left him 12 years later.

The couple's three children were also subjected to sexual abuse and in 2009 the man was sentenced to five years in jail for offences against the family.

Speaking to The Dominion Post, the woman said the details at the trial of her former husband's abuse were so horrific that she suffered a breakdown soon after and was diagnosed with severe depression and post-traumatic stress disorder.

She was granted cover for mental injury but ACC declined to continue weekly compensation because it claimed she was a non-earner when she began counselling in 2007.

In a written district court decision, Judge David Ongley dismissed the woman's appeal despite describing her situation as a "plainly unfair result".

The situation had been caused by the "collision" of two rules affecting entitlement to weekly compensation, he said.

One rule stated that the claimant had to be an earner at the date of injury and incapacity.

But a second rule meant that the date of the injury, in the case of mental injury caused by certain criminal acts, is the date on which the claimant received treatment for that injury.

The woman's application for weekly compensation could only prove that she worked until March 13, 2007, while her first date for counselling for symptoms of mental illness was on April 30, 2007.

With her two daughters still at home, the woman said the decision would have a crippling effect on a strained family.

"I'm sick of having to pay for other people's mistakes, I'm trying to hold the family together and it's not working out very well and now I have this horrible financial burden."

Judge Ongley noted that in many cases someone who suffered mental injury caused by sexual abuse may experience increasingly severe symptoms years after the abuse.

That meant it was likely they might be a non-earner when first seeking treatment.

"To add to the unfairness of her situation, it appears that [the woman] had worked to support her family because of the financial irresponsibility of her husband, and that she was not working at various times because she was dealing with problems that her children had suffered from family abuse by their father, including alleged sexual abuse."

But Judge Ongley accepted that ACC had made all the inquiries that could be expected in light of the information presented.

Leading ACC lawyer John Miller, who represented the woman in her appeal, said about 200 people were in a similar position.

The situation had been caused by a particular High Court decision that ACC ignored until it suddenly decided to enforce it, he said.

Mr Miller was preparing a case involving 30 claimants that would challenge that point of law.

ACC declined to comment.