M&S bras are setting off airport scanner alarms due to the metal used in their underwiring.
Female holidaymakers are facing searches after walking through UK airport security while wearing bras from the high-street retailer.
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Traveller Ann Marchant, 46, told The Sun that she had a "right old search" at Manchester Airport on her way to the Canary Islands.
She said: "The security worker leaned over and whispered, 'M&S?'
"I must have had a really confused look as I didn't know what she meant.
"Then she said, 'No, the bra, it's always M&S bras that set it off'."
The IT worker contacted M&S on Twitter to find out why the bras trigger alarms and the retailer said: "We're not sure, Ann but we're on a mission to get this fixed!"
One tourist took to the social media site and wrote: "Lesson.. Do not go through airport security wearing a new M&S bra.... Talk about a thorough search!"
Another said: "Stansted airport, frisker says, "M&S bra? Metal is very good quality. Always sets alarm off."
Marks and Spencer sells 23 million bras a year.
A spokesperson for the chain told The Sun: "There's 26 different components that go into creating the bras, including the metal underwire. It's uplifting to hear that scanners are detecting this."