An Auckland woman who quit work after being slapped on the bum and repeatedly sexually harassed has been told by the Employment Relations Authority it was partly her own fault, the ERA ruling the woman did not do enough to ensure her own safety.

The decision has caused outrage among employment experts who said the decision was unusual.

"It's absolutely astonishing. She's the victim and they turn round and blame her," said former Green MP Sue Kedgley, one of the founders of the National Organisation for Women.

"It's an incredibly sensitive issue and they're trying to shift the responsibility from the person carrying out the harassment to this rather vulnerable young woman."

The woman was hired by a food service company as a sales cadet in February last year but walked off the job two months later. Both her name and that of the firm were suppressed to protect them. The woman is referred to simply as D.

In her resignation letter she cited numerous examples of sexual harassment by four workmates. Her work colleagues denied most of it, but ERA member Rosemary Monaghan ruled the woman was sexually harassed.

"I find it unlikely that the employees concerned sought deliberately to harass or otherwise upset D. However, I find it likely that their banter and joking behaviour went too far."

In one example, a senior showroom employee arranged a piece of equipment to resemble an erect penis, comments were made about her appearance and there were allegations of offers to "service her needs".

In another incident, a colleague slapped her bottom while she was on a step ladder.

Monaghan rejected her personal grievance claim because she had not complained to her bosses.

That gave the company no chance to stop the harassment.

"D did not display the distress which I accept she felt, so that there was nothing in her observed reactions to alert [her bosses] to the possibility of a problem. D is intelligent and educated. She understood the behaviour was unacceptable and amounted to sexual harassment.

"She did not take steps to raise her concerns about the matter which were not only open to her, but which she was obliged to take under the terms of her employment agreement.

"I do not accept there was a good reason for that. As a result I find that she did not take all practicable steps to ensure her own safety at work."

D claimed her bosses must have known about the harassment and said she did not approach senior managers because she did not trust them.

Monaghan rejected that claim, saying the woman was given an employee manual that included an anti-harassment policy and criticised her because "she probably did not read it".

Monaghan said the woman's "breaches of her obligations [as an employee] were significant".

Employment lawyer Richard Harrison said it was unusual to have a case where sexual harassment happened but the employer was not deemed responsible.

He questioned if it was realistic to expect young women to make complaints.

"It's one thing to say ‘you never raised a complaint' but in reality it's not an even playing field and I think it's unrealistic, particularly for younger employees, to say ‘you should have raised it or gone through a complaints process'," Harrison said.

"People need to be aware it [the ERA] is not the employee-friendly forum some think it is."

The woman's lawyer Daniel Erickson said the experience had been so traumatic for his client she had left the country. She might yet challenge the ruling, he said.