After years of research, the pig industry supply chain launches isotope testing today - an accurate way of checking that pork labelled "British" really does come from British pigs.

Already the testing has uncovered a pack of Tesco pork chops wrongly labelled as British. Further investigation has shown this was a genuine labelling error rather than a deliberate attempt to mislead.

But uncovering wrongly-labelled pork so soon means isotope testing will be taken seriously by the public. And it will ensure food companies strive to make certain that no further mistakes occur.

From 16 September, isotope testing is being introduced as part of British pork supply chain assurance, to add an additional level of reassurance for consumers.

It is intended that 30 randomly-selected products will be tested and that these tests will take place four times a year.

SIRA (Stable Isotope Ratio Analysis) testing will be applied in the retail pork sector initially. It will then be extended to include bacon and ham products and subsequently it will be rolled out into the food-service sector.

The isotope test for pork was developed by the whole industry, including retailers such as Tesco, to show the public that they can trust country of origin labelling.