Nearly 500 food hygiene warnings were handed to businesses in Northampton over the last year - due to problems such as dirty kitchens and separation of foods.
The data from the Food Standards Agency shows the results of food hygiene inspections, over the 12 months to April.
Although most inspections are at restaurants, inspectors also visit farms, manufacturers and catering companies.
In 1,791 inspections carried out in Northampton, there were 494 written warnings handed out.
Any breach of food hygiene regulations can lead to a written warning. Breaches include problems with cleanliness, training of staff, record keeping, washing facilities and separation of cooked and raw foods.
Officials consider the seriousness of the case, as well as the co-operation of the business, before deciding on what action to take.
As well as the written warnings, in Northampton there were 20 hygiene improvement notices and four voluntary closures. Inspectors carried out two successful prosecutions in court, for food hygiene breaches.
High risk scores were given to six businesses. This means they need to be inspected again within six months.
This rating is different from the 0 to 5 score that restaurants and takeaways display in their windows, as it is an indicator of when officials need to assess the business again.
A business which gets a high risk rating is “highly likely” to have breached food hygiene regulations, according to the FSA.
However it could also be because of its trade, such as large scale manufacturers with lots of customers or businesses that carry out specialist procedures.
In total there were more than 150,000 written warnings handed out in England, Wales and Northern Ireland in 2017-18, and 267 successful prosecutions. Scotland collects its data separately.
Nina Purcell, director of Regulatory Delivery at the FSA, said: “It’s encouraging that local authorities have made improvements in the percentage of interventions achieved and are continuing to target their activities at food businesses where food safety risks are the highest or where food fraud is more likely.”
An FSA spokeswoman encouraged people who see bad food hygiene to report it to the council.
In a statement, she said: “You can report poor hygiene practices in a restaurant, store or other food outlet to the business’s local authority at www.food.gov.uk/contact/consumers/report-problem/report-poor-hygiene-practices.”