Restaurants serving sushi and carpaccio-style dishes could be breaking European Union law and run the risk of failing health and safety inspections, Caterer has learnt.

The little-known regulation demands that fish intended for raw or almost raw consumption has to be prefrozen before use for a minimum of 24 hours at a temperature of at least -20°C. Its purpose is to kill any non-visible parasites and nematode (roundworm) larvae.

Restaurants most affected by the law are those serving sushi and sashimi, which uses ultrafresh raw fish.

The regulation was passed in 2004 but it appears that local authorities are now beginning to crack down on restaurants flouting it.

Frederic Serol, operations manager of Marlon Abela's Marc restaurant group, owner of Japanese eaterie Umu, said: "The first we knew about it was last week when a health and safety inspector asked us if we were aware of it. We buy tuna direct from Japan and that has to be frozen, but everything we buy from UK waters, like sea bass, is fresh and will be affected."

Umu carried about 50 sushi and 15 sashimi dishes on its menu and would be forced to pass on any costs associated with outlay on machinery, he added.

A Food Standards Agency spokeswoman said: "Food businesses and operators have a responsibility to make safe anything that's put on the market for public consumption and to be in compliance with the law. It's up to local authorities and their environmental officers to enforce the law."

Shellfish such as oysters are not subject to the regulation, she added.

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