A proposed class-action lawsuit filed by consumers against Starbucks on Oct. 2 in Seattle accuses the coffee giant of selling "sugar-free" beverages that, the suit says, "contain substantial amounts of sugar."
The lawsuit, filed by plaintiffs represented by Hagens Berman law firm, alleges Starbucks "sells eight beverages whose names begin with the words 'Sugar-Free,' even though they contain between 13 and 21 grams of sugar per venti-size serving."
The suit claims that the sugar-free products in question "all contain milk, which contains lactose, a naturally occurring sugar."
"Due to this lactose, the Sugar-Free Products contain approximately 13–21 grams of sugar per venti serving," the lawsuit continues.
Venti is one of Starbucks' larger size options.
While the drinks in question all contain milk, which has naturally occurring sugars, according to Starbucks' website, the added syrups in each drink are sugar free.
The suit claims the eight drinks-- the Sugar-Free Vanilla Protein Latte, the Sugar-Free Caramel Protein Latte, the Sugar-Free Vanilla Protein Matcha, the Sugar-Free Caramel Protein Matcha, the Iced Sugar-Free Vanilla Protein Latte, the Iced Sugar-Free Caramel Protein Latte, the Iced Sugar-Free Vanilla Protein Matcha, and the Iced Sugar-Free Caramel Protein Matcha-- contain well over the amount of permissible sugar allowed in the reference amount customarily consumed to be considered "sugar free"
"We believe these claims have no merit," a Starbucks spokesperson said in a statement to ABC News on Tuesday.
Federal code cites less than 0.5 grams of sugar per serving is the threshold to be labeled sugar-free, according to the suit, and reflected in a code of federal regulations found online.
The suit goes on to claim, "The 21 grams of sugar contained in a venti Sugar-Free Caramel Protein Matcha is roughly equal to five teaspoons of sugar. This is almost as much total sugar as is contained in a standard Kit Kat bar."
The statement continued, "Starbucks has consistently and clearly provided information about its protein beverages, sugar-free options, customization choices, and nutritional content across product announcements, menus, marketing materials,Starbucks.com and the Starbucks app, and we intend to vigorously defend ourselves in this matter."
The lawsuit called the names of the "sugar-free" drinks "false and misleading"
The eight drinks in question, which have "sugar-free" in the title, are listed under a menu tab titled "No Added Sugar Options."
Each of the eight options, as the lawsuit notes, has its sugar contents listed on the individual beverage page for each drink. The sugar contents, along with calories, fat and protein statistics, are visible once the viewer scrolls down on the page.
The lawsuit also accused Starbucks of not properly using a required calorie disclaimer with the "sugar-free" labeling.
ABC News has reached out to the plaintiffs' attorneys for additional comment.
ABC News' Taylor Dunn contributed to this report.