Illegal meat imports, thought to have caused the 2001 foot and mouth outbreak, are still flooding into Britain, according to an official watchdog.

A report from the National Audit Office (NAO) has revealed that some 12,000 tonnes of meat and meat products are still illegally entering the country each year.

The 2001 epidemic, most likely to have been caused by the inclusion of illegally imported contaminated meat in pigswill, cost the country around £8 billion.

Border controls, operated by Customs, have since been tightened in a bid to stop illegal imports of animal products from outside of the European Union.

But NAO head Sir John Bourn said Customs should prosecute more cases and consider introducing on-the-spot-fines.

The report said that only a "very small amount" of the illegal imports is likely to be infected with disease, but added that the economic consequences of infected material getting into the animal food chain "could be severe if this were to result in a major disease outbreak".

"The foot and mouth disease outbreak showed how important it is to prevent infected meat entering the country illegally." said Sir John.

"Since taking over responsibility for controls over imports of animal products from outside the EU, Customs has improved our protection.

"My recommendations should help to tighten controls further."