The NBA has written to the major retailers claiming that mixing packs of meats of different origin in the chiller breaches EU regulations.
It said it was alarmed at the number of reports it had received of UK beef being sold from the same section of the chill cabinet as imported beef and urged members to report such cases to Trading Standards.
NBA chief executive Robert Forster said many consumers could have picked up packs assuming them to be British when they were not.
"UK beef is attractive to purchasers who are more likely to pay a premium. If they have mistakenly purchased imported beef instead of home-produced, they can consider themselves to have been deceived by the co-mingling arrangement."
However, major retailers denied mixing countries of origin in their beef chill cabinets.