Shoppers who have bought the Waitrose 1 white and milk chocolate bars weighing 85g and costing £1.60 are urged not to eat the treats because of a risk of choking.
The affected varieties are White Chocolate, White Chocolate with Matcha Tea & Pistachio, Milk Chocolate with Pistachio, Almond & Hazelnut and Milk Chocolate with Feuilletine & Sea Salt.
All have the best before date of July 2018 and include all batch codes.
A Waitrose spokesman said: “We are recalling the above products, as there is the potential that a small number of bars may be contaminated with pieces of plastic.
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“Customers who have purchased any of the above products should not consume them, but return them to Waitrose for a full refund.
“We apologise for any inconvenience to our customers.”
The Food Standards Agency added: “Waitrose is recalling four varieties of Waitrose 1 chocolate bars because they may contain pieces of plastic.
“No other Waitrose products are known to be affected.
“Products may contain pieces of plastic which could represent a safety risk.
“If you have bought any of the above products do not eat it. Instead, return it to the store from where it was bought for a full refund.”