Sheep industry leaders have called for an urgent meeting with Tesco after the retail giant told customers British lamb was out of season - at the peak of domestic production.
National Sheep Association chief executive Phil Stocker said he wanted talks with Tesco chief executive Philip Clarke to "ensure Tesco's offering of UK lamb is optimised".
It came after Lancashire sheep farmer Linda Allen received New Zealand lamb leg steaks in her Tesco home delivery order at a time of year when UK lamb is plentiful and delicious.
Mrs Allen was shocked when an email conversation with Tesco customer services resulted in three members of staff communicating the same message that UK lamb was "not in season".
Mr Stocker said Tesco should deliver on its commitment to UK agriculture.
"I have written to Philip Clarke today to say Mrs Allen's home shopping experience was bad enough, but the explanation she received when she questioned it was even worse," he said.
"This incident occurred in late September, a month when UK lamb production is at its peak and quality is at its best."
"For Mrs Allen to be told lamb is 'out of season' is astonishing and either purposefully misleading or a case of Tesco staff being completely unaware of reality. It is unacceptable either way."
Tesco's response "flew in the face" of everything Mr Clarke had been saying publicly since the horsemeat scandal earlier this year, said Mr Stocker.
After Tesco beefburgers were found to contain horsemeat, Mr Clarke pledged that the retailer would shorten its supply chains, get closer to UK producers and support UK farmers.
Mr Stocker said: "The recent evidence we have seen shows this is not happening or that any progress is miserably slow.
"I have therefore asked Mr Clarke for a meeting at his earliest convenience."
While the UK always sees a seasonal peak and trough of numbers of lambs marketed, the nature of UK farms meant there was never a time when UK lamb was out of season.
Tesco has acknowledged it made a mistake when responding to Mrs Allen.
A Tesco spokesperson said: "We are British agriculture's biggest customer and we are confident that we source more British lamb than any other UK retailer."
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