More than 150 restaurants, pubs, shops and takeaways in and around Norwich have been told by food inspectors that they need to improve their standards of hygiene.

Recent figures show the number of food premises in the city which are 'broadly complaint' with food hygiene law has dipped.

And that means hygiene in about 10pc of businesses which sell food is not up to scratch, according to inspectors.

Among the hygiene contraventions discovered by inspectors last year were: • A shop selling food and drink which was 18 months out of date

• Bags of 'raw' meat found at the bottom of an ice-cream freezer

• A restaurant with mouldy and dirty taps

• A shop which had a rat and cockroach infestation and where some of the food had been gnawed by rodents

• A takeaway where food was being defrosted in a dirty sink

• A cafe where leftover, reheated soup was cooled, refrigerated and used the next day

• A pub where the chef was seen by inspectors handling raw bacon directly next to open salad, until reminded

what he was doing was wrong

• A takeaway which had an 'active rat infestation' in its cellar cavity walls

The dip in standards has led environmental health officers at Norwich City Council to take the 'unprecedented step' of writing to almost 300 food premises to warn them they are due to be inspected, because of fears standards are slipping.

And Jaan Stanton, food safety manager at Norwich City Council, said he would like to see food premises legally required to display their food hygiene ratings, as he believes that would help raise standards.

The city council was the first local authority in the UK to have its own public food hygiene rating scheme and was the first to sign up to the Food Standards Agency's national scheme in 2010.

After a premises has been inspected an overall number rating, from zero (the worst) to five (the best) is awarded, based on food safety standards found at the time of the inspection.

Three areas are assessed with regard to compliance with food law - food hygiene, structure and cleanliness and confidence in management.

Since 2009, the number of broadly compliant food business - those which get a rating of 3 or above in the checks - has increased by about 2pc year on year.

But the most recent figures showed a drop in the number achieving that rating, from 91pc in 2011/12 to 89.9pc.

A city council spokeswoman said: 'It was apparent that some businesses were failing to keep up to date with their management checks and in certain cases standards of food hygiene and cleaning had also slipped.'

As of January this year, there were 153 food premises in the city which are not broadly compliant, having a rating of 2 or below and which, according to the inspectors, require 'at least some degree of improvement'.

The council said one of the reasons for the slip in standards is because a large number of inspections are being conducted at businesses which have not been inspected for some time.

Mr Stanton said: 'I don't think it's a question of the novelty wearing off, but the issue dips in and out of the consciousness of businesses.

'I know the scheme recently featured on the BBC programme The Food Inspectors and the Food Standards Agency were very pleased about that.

'But there is probably a point at which you won't any major further improvement until the introduction of compulsory display of the ratings. 'We would very much welcome that, as it would provide the spur to get improvements once again.'

The dip in performance led the council to take what they called an 'unprecedented step' of writing to 272 businesses which are due an inspection before the start of April, to warn them that inspectors would soon be on their way.

A council spokeswoman said: 'Each was reminded that their inspection was due soon and told of some of the common faults that had contributed to recent low scores. All subsequent inspections were, and continue to be, unannounced.'

The city council spokeswoman added: 'None of us can take food safety for granted. Every year around a million people get food poisoning in the UK and regrettably some of these people die.

'Keeping standards high not only requires an effort on the part of the food businesses operator but also a commitment from the city council to support businesses with advice and guidance where appropriate.'

Twenty notices were served on businesses which contravened food safety laws last year. The council accepted voluntary closure from three of them, while one - The Asian Bazaar in Magdalen Street - was closed down using an emergency prohibition notice.

Mr Stanton said the council would always look to avoid prosecuting businesses if possible, but said there were some prosecutions in the pipeline.

He added key advice to businesses, along with general cleanliness, included: Keeping management checks up to date, including a daily diary; to make sure there is no cross contamination which could lead to e-coli; to ensure sinks are clean, with soap dispensers kept topped up and handtowels regularly changed; and to make sure food is stored at the correct temperatures.

While some food businesses do display their award certificates so the public can see how they fare, all ratings can be found on the city council's website at www.norwich.gov.uk/environment/EnvironmentalHealth/FoodSafety/FoodHygieneRatings/Documents/FoodRatings.html