Prince Charles' organic food company is selling New Zealand lamb instead of local fare.
Owner of meat processing plants in Hastings and South Wales, Craig Hickson, has sprung to the defence of the New Zealand product following criticism it is "over-fat and over-priced".
The Duchy Organic range - set up by the Prince of Wales - is selling New Zealand lamb because local lamb was temporarily unavailable, the South Wales Evening Post reported.
The Duchy brand is a partnership between supermarket chain Waitrose and the Duchy Originals company set up by Prince Charles in 1990.
The Prince of Wales Charitable Foundation receives a percentage of every sale made by Waitrose, which has 340 stores.
"I've been lambing for the past eight weeks battling the elements, then I go into my local Waitrose to find New Zealand lamb for sale under the Duchy Organic label," Welsh farmer Gethin Havard told the South Wales Evening Post.
He said it was inferior to Welsh lamb and "over-fat and overpriced".
Mr Hickson, the owner of Progressive Meats, said New Zealand lamb was likely leaner than its UK equivalent and "certainly not fatter".
"New Zealand farmers had the right financial signals to significantly lean up our lamb from what it was 30 years ago," he said. "If anything now it is consistently lean - right through a wide weight range as a generality - and it is very rare for us to see over-fat lambs presented for slaughter."
It was also far from overpriced, being cheaper than its UK equivalent thanks to supermarkets discounting up to 70 per cent of New Zealand lamb for promotions to drive shoppers through doors, he said.
"It is not something we are overly happy with because it impacts upon the image.
"Our view is it would be significantly and generally under-priced. It represents to the consumer over there significantly good value for money, relative to Welsh lamb."
However, compared with pork, chicken and many beef cuts, it was a more expensive meat.
The Duchy New Zealand lamb, because it was under an organic label, was likely to be more expensive, more variable and of very small quantity.
"It would not be representative of New Zealand lamb."
A Duchy of Cornwall spokeswoman said Waitrose leased the Duchy Organic brand.
A Waitrose spokesman said outside the UK season it sourced from overseas "rather than not offer an organic choice to our customers".