The WA retail union say workers are being assaulted physically and verbally every day, after shocking mobile phone footage emerged from Lakelands McDonalds that shows a teenage girl spit on a worker.
The footage emerged on social media on a local Facebook group on Wednesday, showing a group of young girls causing a commotion at the premise by attempting to attack a staff member behind the counter.
One of the girls spat at a male employee, before leaving the restaurant.
Mandurah Police Acting Senior Sergeant Ryan Van Der Heide told the Mandurah Mail the incident happened about 10.15pm on Tuesday.
"Police have been made aware of the incident and are making inquiries into the matter," he said.
"No-one has been charged at this time."
Shop, Distributive & Allied Employees' Association (SDA) WA secretary Peter O'Keeffe said violent and abusive behaviour by customers is a "serious workplace safety issue".
"This behaviour impacts the physical and mental health of fast food workers," he said.
"It's clear that on a daily basis fast food workers across the state are being subjected to constant verbal abuse, threats of violence and in some cases, actual physical assault.
"We commend the professional and calm approach taken by both the worker behind the counter and the security guard during this disgusting incident.
"Hopefully the two culprits in this case will feel the full force of the law for their disgraceful behaviour.
"Our message to the public is that this behaviour has got to stop. Copping abuse is not part of the job. No one deserves a serve."
The WA retail union found 87 per cent of workers had experienced verbal abuse or aggressive behaviour, after interviewing more than 1000 fast food workers in December 2018.
Mr O'Keefe said the survey showed fast food workers have received death threats, threats of rape and had items such as cigarettes and hot coffee thrown at them.
A McDonald's spokeswoman told WA Today the restaurant had provided CCTV footage to police and "encourage them to take appropriate action against these customers".
"Behaviour like this in our restaurants in completely unacceptable," she said.
"We will continue to take all necessary steps to ensure the safety of our crew."