However, Tesco was adamant that one of its largest suppliers in New Zealand, Silver Fern Farms in Fairton, should stop using dogs to herd sheep into the abattoir.

Unlike in Britain, most abattoirs are attached to farms in New Zealand, ensuring the farm does not need to truck its flock down the motorway to a slaughterhouse.

The supermarket wants the shepherds to wave their arms, beat sticks or wave flags, to move the sheep into the abattoir.

The surprise order from Tesco, which comes into force next week, came to light thanks to a letter sent to the Daily Telegraph by an upset reader.

Mick Petheram, one of the shepherds, said: "New Zealand sheep are used to dogs, they know dogs. There's more stress in a human herding and manhandling them, waving their arms and beating sticks. Dogs are part of a sheep's life. This is absolute baloney."

He said that he and his fellow workers would have to sell their dogs, or worse, put them down. "We'll be desperately trying to sell them, but most of us will end up putting down three or four each. These are bloody good dogs. Taking away our dogs is like taking a hammer away from a builder; we can't do our job without them," he said.

New Zealand is the biggest source of lamb in Britain at this time of year, and it is understood that the Silver Fern Farms is one of Tesco's biggest suppliers.

It was visited by Tesco buyers earlier this year, who were "upset" at seeing the dogs "running riot", according to a spokesman for the supermarket.

The National Farmers' Union said that it was not aware of any research indicating that farm animals suffered stress because of sheepdogs.