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Bottled lemon juice is a $100 million business but the National Consumers League is asking the Food and Drug Administration to put the squeeze on four brands that the group says are passing off a watered-down product as 100 percent lemon juice.

The National Consumers League tested samples of four different products labeled 100 percent lemon juice.

After testing two bottles each of NaturaLemon 100% Lemon Juice from concentrate - Natural Strength, Lira 100% Lemon Juice from concentrate, Lemon Time Lemon Juice from concentrate and Pampa, the group's lab found that NaturaLemon contained about 35 percent lemon juice; Lira, about 25 percent; Lemon Time, about 15 percent; and Pampa, just 10 percent.

"We wrote them [the FDA] in March," said Sally Greenberg, the executive director of the National Consumers League. "We haven't heard anything. When the FDA doesn't respond and they have got everything together - all the evidence there - it sends a signal to the industry that you can cheat consumers and you can rip them off and nothing is going to happen."

The FDA prohibits adding excessive water to juice.

Greenberg said these companies take the risk of cheating consumers to save money.

"Lemons are expensive," she said. "Unscrupulous companies decide 'Hey, we're going to save ourselves a lot of money. We are going to mislabel the product and we're going to rip consumers off. In the meantime, we are going to pocket the change.'"

ABC News found these four brands in discount stores and dollar stores.

"They are marketed to those kinds of stores, to people who don't have a lot of money to spend and may not have enough information," she said.

Castella Imports, the distributor of Lira, said that its product met the government definition of lemon juice.

"The product's ingredients include lemon juice from concentrate, water, citric acid and lemon oil, along with preservatives and emulsifiers - ingredients that are listed clearly on the label and all of which are included in the U.S. Food & Drug Administration's Code of Federal Regulation for ingredients in lemon juice.

"Furthermore, our lab tests indicate that Lira contains appropriate concentrations of dissolved lemon solids to meet the FDA definition of lemon juice. There is no intent to mislead consumers and in fact, we are currently seeking FDA approval of revised front-of-package labeling that we hope will clear up any questions consumers might have," Castella said in a statement to ABC News.

NaturaLemon's distributor said that it would investigate the NCL's claims.

"We are very surprised at this result and we are investigating. We've been in business for over 30 years and we have a perfect reputation in the industry.

"Again, we are very surprised and investigating," said Hope Iovine, the general manager of Sirob Imports.

Calls to the other products' distributors and manufacturers were not returned.