(The boss) said "stamps off" and made sure that the stamps were off and there was no traceability

Former meat company employee

The firms - Hughes meat company in Bangor, and Arfon meat company in Caernarfon - exposed in the programme provide meat to many butchers and restaurants throughout the north Wales county of Gwynedd.

They promote themselves as companies who support local farmers and deal with Welsh produce.

But former employees claim that the re-labelling process has been going on for a long time and has been done in order to keep costs down and maximise profits.

One man - who did not want to be identified - insisted this was far from the truth.

Practice condemned

"When the meat from Ireland came in the boss let us know it was Irish and said "stamps off" and made sure that the stamps were off and there was no traceability," he said.

Organisations set up to bolster the Welsh food industry have condemned the practice.

Welsh Lamb and Beef Promotions has said the case makes a mockery of the traceability rules designed to ensure customers can trace meat from the supermarket shelves back to its farm of origin.

"At the moment there is a very strong voluntary code we try to impose on the industry but, of course, our ability to impose it is not backed by legal abilities such as trading standards," explained Welsh Lamb and Beef Promotions Director Don Thomas.

"Consumers are extremely worried about the origins of the product that they are buying and I think they expect the labelling to have 100% integrity."

A shareholder of the one of the companies implicated said that he would be asking for his money to be returned.

Full details of the investigation can be seen on Taro Naw at 2100BST on Monday on S4C.