CCTV footage has emerged of an alleged assault of a west Auckland Burger King worker.

Abby Holland says she was hit during a disagreement with management and the workers' union says the incident is just the tip of the iceberg.

The 18-year-old says that's when her manager smacked her in the back of the head while hustling her out of the kitchen.

"I didn't say anything to her, she just did it. And I turned around and she said to me, 'Do you want me to hit you again?'" recounts Ms Holland.

"I was in shock, I didn't understand."

The 18-year-old says the incident stemmed from a dispute over a faulty air conditioning unit at the Lincoln Road store.

She says the kitchen was too hot, and she had been using a thermometer to take a temperature reading when things turned sour.

"One of the other managers on shift came up and started snatching it out of my hand saying I wasn't allowed to do it and that I needed to get back to work because the customers are more important."

Ms Holland says she was scared to return to work, and claims she was threatened by other colleagues who disagreed with her speaking out.

Unite Union believes Burger King is fostering an unsafe culture.

A spokesperson says "the company has a really bad track record of eliminating health and safety risks".

It's not the first time the fast food chain has come under fire for the treatment of its staff.

In 2012 there were protests over concerns workers were being pressured to leave the union.

The manager at the centre of the latest incident has been formally cautioned by police.

Burger King claims some of the allegations are inaccurate, but wouldn't specify exactly which ones. It says it takes health and safety seriously, and investigates all incidents.

Newshub.