An Indian-American lawyer has launched a class-action lawsuit against burger behemoth McDonald's, alleging that the company has misled vegetarian consumers for more than ten years over its beefy French fries.

Lawyer Harish Bharti, who avoids meat because of his Hindu religion, filed the suit in the King County Superior Court, Seattle, on behalf of the million-strong Hindu community in the US and the country's 15 million vegetarians. He has declined to name the two main plaintiffs in the case, but revealed that he has received many calls from Hindus and vegetarians seeking to sign up to the lawsuit. Bharti has said that anyone who ate the offending fries after 1990 while believing them to be meat free could be party to his suit, and the other suits he plans to file elsewhere in the US.

Bharti, who has lived in the US for 18 years after emigrating from Patiala, revealed that he decided to sue after religious guru Dr Raganand ate the fries while visiting him, then found that the company uses beef tallow "for flavour enhancement."

In the US, the average McDonald's restaurant sells 87,600 pounds of French fries annually, which tallies up to 1.05bn pounds of fries nationwide every year. "Upon information and belief, a sizable percentage of such French fries are consumed by vegetarians under the belief that the fries are vegetarian," Bharti argues.

"They shouldn't be deceiving people," he said. "This is [the] first such class action lawsuit against McDonald's. They are more powerful than a country and it is time they are taught a lesson."

Bharti is claiming "injunctive relief to stop this practice" and compensation to the tune of "millions of dollars," arguing that the firm "secretly" laced its fries with beef fat while stating otherwise in its publicity.

He describes McDonald's advertising as "the ultimate height of corporate greed," and cites an e-mail in which the company discloses its suppliers use tiny amounts of beef flavouring, despite advertising that its fries are made with "100% vegetable oil."

Following a health controversy in the early 1990s, the CEO of McDonalds guaranteed that the fries would be cooked in vegetable oil. It seems that beef fat is still making its way into the fries, however, listed on the company's web site under the ominous description "natural flavour." Bharti says that an email from Megan Magee, an employee in McDonald's customer-satisfaction department, confirmed that this was the case.

"By concealing the existence of beef in their French fries and allowing plaintiffs [...] to consume the French fries in violation of their sincere religious beliefs, the conduct of the defendants was so outrageous in character, and so extreme in degree, as to go beyond all possible bounds of decency," says Bharti in the lawsuit.

Based in Oak Brook, Illinois, McDonald's has refused to comment on the lawsuit, but a spokesman insisted that despite the publicity surrounding the use of "100% vegetable oil," the company had never claimed that the fries were vegetarian. He added that consumers could be given information about all the ingredients, but evidently they have to ask.