Anheuser-Busch InBev's St. Louis-based brewery routinely adds extra water to its finished products to produce malt beverages with significantly less alcohol content than displayed on its labels, violating state statutes on consumer protection, according to a complaint filed Tuesday in federal court in Philadelphia.

Similar lawsuits were filed in federal courts in New Jersey and San Francisco.

Anheuser-Busch InBev NV is the world's biggest brewer.

"AB's customers are overcharged for watered-down beer and AB is unjustly enriched by the additional volume it can sell," Thomas and Gerald Greenberg said in the Philadelphia complaint.

The claims against Anheuser-Busch are "completely false," Peter Kraemer, the company's vice president of brewing and supply, said in an email.

"Our beers are in full compliance with all alcohol labeling laws," Kraemer said. "We proudly adhere to the highest standards in brewing our beers, which have made them the best-selling in the U.S. and the world."

Budweiser, the No. 3 beer in the U.S. in 2011, was introduced in 1876 when company founder Adolphus Busch set out to create a national beer brand, according to the Anheuser-Busch website. Each batch of the beer, which blends American aroma hops with barley malts and rice, follows the same family recipe used by five generations of brewmasters, according to the website.

AB InBev, the maker of Budweiser and Stella Artois, controls 39 percent of the U.S. beer market. The company is seeking government approval to buy the rest of Grupo Modelo SAB, Mexico's largest beermaker, for $20.1 billion. The Modelo brands account for 7 percent of the U.S. market.

AB InBev shipped 98.5 million barrels in the U.S. in 2011, according to Beer Marketer's Insights.