(Reuters) -Diageo on Monday filed an initial response to a lawsuit accusing the spirits giant of misleading U.S. consumers about the purity of some of its popular tequila brands, calling the claim "baseless".

The company, which also owns whisky brands such as Johnnie Walker, said in the filing the complaint provides no evidence to support the claim that its Casamigos and Don Julio tequilas are not "100% agave".

All bottled tequilas of these brands labeled as "100% agave" are made from 100% Blue Weber agave and undergo a rigorous production and independent, multi-step certification process, the company said.

One of the lawyers for the plaintiffs, Steve Berman of Hagens Berman Sobol Shapiro, said he does not have a response yet, while Robert Tolchin of The Berkman Law Office did not immediately respond to a Reuters request for comment.

In May, a class action filed in federal court in Brooklyn accused the company of falsely advertising Casamigos and Don Julio tequilas as "100% agave," claiming they contained other alcohols and failed to meet U.S. or Mexican standards for pure tequila.

Two similar lawsuits were filed against Diageo in California and Florida in the same month, with one alleging that some versions of Casamigos and Don Julio contained between 33% and 42% agave-derived ethanol, citing carbon isotope testing commissioned by the plaintiff.

Diageo has called the claims "outrageous and categorically false", adding it will "vigorously defend" the quality of its tequilas in court.

The lawsuits highlight a broader industry dispute over tequila purity, with "additive-free" claims prompting pushback from Mexico's Tequila Regulatory Council (CRT).

The CRT has warned some producers using the "additive-free" label that their export licenses could be revoked unless the claim is removed from packaging and marketing, according to a copy of one letter sent to a brand and seen by Reuters.

The CRT called the "additive-free" label misleading, noting that tequila can legally contain additives such as colorants and sweeteners up to 75 grams per liter of sugars or similar ingredients, according to official Mexican regulations.

(Reporting by Anuja Bharat Mistry in Bengaluru and Emma Rumney in London; Editing by Devika Syamnath)