A Dominos pizza shop in Sydney's west has been described as having committed one of the worst breaches of food safety and hygiene in New South Wales.

The store in Quakers Hill has been fined almost $120,000 after investigations by the state's Food Authority, following reports from customers who suffered food poisoning.

Primary Industries Minister Steve Whan says conditions inside the store were appalling.

"They had evidence of significant infestation of cockroaches and also very poor hygiene of cleanliness habits," he said.

"I'm told by our experts at the Food Authority that they're a prime candidate for spreading food-born illnesses and that's why they've been given such a big fine.

"There are always people who don't do the right thing unfortunately and we need to make sure that we can protect people from food-born illnesses.

"Things like food poisoning are not insignificant. There are people every year who die of food poisoning and food-related diseases."