Twenty-two food outlets may be putting diners at risk having earned a zero hygiene rating - the lowest possible score for food safety and cleanliness.

Fly infestations, out of date food, dirty surfaces and cross-contamination were just some of the issues highlighted by inspectors.

A zero star rating indicates ‘urgent improvement is necessary’, and inspectors have the power to close down a business if they think there is an immediate risk to the public.

Scroll down for the full list

Restaurants are judged on three areas: the hygiene of the food served, the cleanliness of work surfaces and appliances, and how well management keeps cleaning records and acts on criticism.

Outlets with a zero rating are likely to have scored badly against all three criteria, says the Food Standards Agency, which oversees the national food hygiene rating scheme.

"In my opinion things are generally improving. The worst places will have closed and businesses are getting more competitive - bad hygiene just isn't tolerated now by the public" - Peter Lincoln, food and safety team leader

The 22 Kent premises with a zero score include 14 restaurants and takeaways and eight food shops.

It's a tiny proportion of the 10,729 food outlets in the county, 94% of which have three stars or above, according to the Food Standards Agency.

But the potential dangers of dirty surfaces and cross-contamination can have serious consequences, including various types of food poisoning.

Campylobacter is the most common cause of food poisoning in the UK. You can’t see it, smell it or even taste it on food, but it can make people ill for several days.

A common cause of campylobacter poisoning is cross-contamination from raw poultry.

Local authorities are responsible for monitoring food safety standards, and most premises are visited once a year, or more regularly if a problem has been identified.

Full list of zero-rated businesses (accurate as published March 2015)

Balas Little Mart, Gravesend

Frankies, Westgate On Sea

Norton Cross Service Station, Norton

Stonar Cafe, Sandwich

The Bull Inn, Newington

The Oak, Charing Kent

Yellow Fisherman/Raj Curry House, Westwell

Bassant, Gravesend

Deal Direct Fish, Deal

Grand Appetito, Tonbridge

Kings Fried Chicken, Chatham

Milestone Kebab, Stone

My Cafe, Chatham

Napier Convience Store, Gillingham

New Favoured Chicken, Gillingham

Northdown Road Groceries, Margate

Pyus Afro Carribean Cash And Carry, Sittingbourne

Ringlestone Farm Shop, Maidstone*

Royal Dragon, Birchington

Ruby Chinese Takeaway, Gillingham

Rumpy, Dartford

Shapla Tandoori, Sheerness

Twin Dragon, Folkestone

Councils say in most cases their inspectors will work with a business to help it improve standards as quickly as possible, offering advice on how to improve specific problems.

Swale, Tonbridge and Malling, and Maidstone councils share inspection services. Peter Lincoln is the leader of the team covering the three areas.

He explained that most outlets were happy to accept advice: "The vast majority of businesses are fine and we try to have a reasonable conversation. There are a few exceptions, but we try to persuade businesses to comply in the first instance.

"In my opinion things are generally improving. The worst places will have closed and businesses are getting more competitive - bad hygiene just isn't tolerated now by the public."

If problems at a food outlet are so bad people are at serious risk, inspectors can close down the business on the spot using a hygiene emergency prohibition notice.

This requires the owner to appear at a magistrates' court to put their side of the story before the premises can be reopened.

Ashford council offered several hypothetical cases where drastic action would be necessary.

A spokesman said: “Some examples of when closure is appropriate are where there is an infestation by pests, lack of hot water, defective equipment serious enough to result in the actual contamination of food or a significant risk of contamination.”

Fortunately, such serious cases are few and far between. The last time Mr Lincoln remembers using such an order was five years ago for a particularly bad cockroach infestation.

He said: "They are creatures that normally come out at night but here it was day time and they were everywhere. The cockroach infestation was directly affecting the food."

But sights like this do not stop Mr Lincoln from enjoying a meal out, even though he admits to occasionally scrutinising the forks.

He said: "I still go out to eat. I try to leave my work in the office, but it's not always easy."

All the hygiene rating information comes from the Food Standards Agency website.

* Since the inspections in this story were made, the Ringlestone Farm Shop has been removed from the list.

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