KFC has filed a lawsuit against Church's Texas Chicken for allegedly violating its trademark rights by using the term "original recipe" in its advertising.

The lawsuit, filed last week in federal court in Texas, claims fast-food rival Church's "abruptly" started using the branding to promote its fried chicken in September. The ads promoted across television, social media and Church's website state "Our original recipe is back" along with photos of their fried chicken line.

KFC said it sent a letter to Church's in October objecting to their use of the phrase, but it was ignored.

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KFC has used the trademarked phrase "original recipe" for over half a century. In the lawsuit, the company stated it continues to be a cornerstone of KFC’s advertising to promote its fried chicken made with "a secret blend of 11 herbs and spices resulting in a unique, signature flavor."

"That combination of 11 herbs and spices is one of the most well-known, iconic trade secrets in the food industry. And it is that combination of ingredients that KFC has promoted with the original recipe mark," the lawsuit stated.

KFC told the U.S. District Court for the Eastern District of Texas that Church's continued use of the trademarked phrase in its ads is likely to confuse consumers and have a negative impact on their brand.