A Burger King Whopper hamburger is displayed on April 05, 2022 in San Anselmo, California. A federal lawsuit has been filed and is seeking class-action status alleging that fast food burger chain Burger King is misleading customers with imagery that portrays its food, including the Whopper burger, as being much larger than what is actually being served to customers. (PHOTO /AFP)

A US judge has rejected Burger King's bid to dismiss a lawsuit claiming that it cheated hungry customers by making its Whopper sandwich appear larger than it actually is.

US District Judge Roy Altman in Miami said Burger King must defend against a claim that its depiction of Whoppers on in-store menu boards mislead reasonable customers, amounting to a breach of contract.

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Customers in the proposed class action accused Burger King of portraying burgers with ingredients that "overflow over the bun," making it appear the burgers are 35 percent larger and contain more than double the meat that the chain serves.

"The plaintiffs' claims are false", Burger King said in a statement on Tuesday. "The flame-grilled beef patties portrayed in our advertising are the same patties used in the millions of Whopper sandwiches we serve to guests nationwide"

Burger King, a unit of Restaurant Brands International, countered that it wasn't required to deliver burgers that look "exactly like the picture," but the judge said it was up to jurors to "tell us what reasonable people think."

In his decision made public on Friday, Altman also let the customers pursue negligence-based and unjust enrichment claims.

He dismissed claims based on TV and online ads, finding none in which Burger King promised a burger "size," or patty weight, and failed to deliver it.

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"The plaintiffs' claims are false," Burger King said in a statement on Tuesday. "The flame-grilled beef patties portrayed in our advertising are the same patties used in the millions of Whopper sandwiches we serve to guests nationwide."

People look at the menu at a counter of a Burger King outlet in New Delhi on August 17, 2023. Soaring vegetable prices after a bad harvest have prompted Burger King's Indian outlets to take tomatoes off their menu items, following in the footsteps of other fast food giants. (PHOTO / AFP)

A lawyer for the plaintiffs was not immediately available for comment. Earlier efforts to mediate a settlement proved unsuccessful.

McDonald's and Wendy's are defending against a similar lawsuit in the Brooklyn, New York federal court. The plaintiffs' lawyer there on Monday cited Altman's opinion to justify letting that case continue.

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Taco Bell, a unit of Yum Brands, was sued last month in the Brooklyn court for selling Crunchwraps and Mexican pizzas that allegedly contain only half as much filling as advertised.

Each lawsuit seeks at least $5 million in damages.

The case is Coleman et al v Burger King Corp, US District Court, Southern District of Florida, No 22-20925.