By Luke Hanrahan, ITV Reporter.
In Wales, on the front door of every restaurant and takeaway they are a familiar sight.
Food hygiene star ratings are a legal requirement and expose the filthiest businesses with a zero score - while rewarding the safest and cleanest with a 5 star rating.
The rest of the country has not yet made it mandatory for restaurants to display these ratings. The FSA ratings scheme, known as "scores on the doors", tends only to be displayed by some of the restaurants that receive high ratings.
But in London alone, there are a total of 358 restaurants with a zero Food Standards Agency Rating.
Those food outlets are deemed to have serious failings - anything from safety, structure, cleaning and management. They all require "urgent improvement", according to the Food Standards Agency.
One of the biggest issues we find in Westminster is cross contamination, that's raw meat being in contact with ready to eat food. If you have raw meat in contact with things like sandwiches - the pathogens on that raw meat could be in contact with the sandwich. Things like salmonella, Campylobacter, ecoli - bacteria that will make you ill.
Restaurants are not always automatically closed down once they receive a low rating.
They are only closed down when the food poses an immediate risk to the public. The owners have 14 days to appeal the rating - if they decide not to many are allowed to stay open under the proviso that they will improve safety.
Ratings are publicly available, but currently it is not mandatory to display them.
The FSA is responsible for collating the ratings, which are provided to them by 'food teams' at local authorities.
These ratings are currently available on the FSA website.
There are now calls to make it mandatory for restaurants in England to display their scores so the public can make better-informed decisions.
In London, environmental health officers check food hygiene at restaurants every single day, carrying out inspections on behalf of councils.
One of the key sources of information is from the public. They smell, or they hear or see an issue. On one occasion we received a complaint regarding a business in Westminster saying there was a smell of sewage within a restaurant.
There are restaurants in London with zero ratings who display inaccurate FSA accredited stickers. In the eyes of the law the restaurant could be seen to be seeking to influence the customer's purchasing decision by providing false and misleading information. The question is, should restaurants have to display their score on the door?
A spokesperson from the Food Standards Agency told ITV News they think restaurants should, and they are building the case to convince the government to change the law.
Mandatory display of food hygiene ratings offers additional benefits for consumers and those businesses that have good hygiene standards and further encourages other businesses to raise their standards. We are pleased that there is already mandatory display in Wales and also pleased that the Northern Ireland Assembly is considering legislation that will make it mandatory for businesses there too.
If you think a restaurant near you is displaying an incorrect rating, get in touch: firstname.lastname@example.org.