Tesla executives said they decided not to use Mr. Fisker’s design and were starting over on the design for White Star when they discovered that Mr. Fisker was going into competition with them. The design switch caused a three- to six-month delay in production of the car, which is now scheduled to go on sale in 2010, the company said. Tesla is building a factory in New Mexico to manufacture the sedan.

Image Henrik Fisker, the founder of Fisker Automotive, with his electric car, the Karma. Credit... Gary Malerba/Associated Press

“It caused a slight delay in White Star because we could not use the Fisker styling,” said Elon Musk, chairman of Tesla. “The styling was substandard compared to what he unveiled for his product. He gave us an inferior work product, and it’s obvious why.”

Tesla has scrambled to come up with a new design with some help from Lotus, the maker of the bodies for the initial Tesla Roadster. Mr. Musk said that he was leading the effort.

“‘I’m not really a car designer,” said Mr. Musk, who was one of the founders of PayPal and started SpaceX, a developer of spacecraft. “We’ll see what people think of cars designed by me versus Fisker; it’s the amateur versus the professional.”

The Tesla lawsuit seeks to stop Mr. Fisker from using Tesla design documents, along with a return of the money from the contract and unspecified punitive damages.

Having previously designed cars for BMW and Aston Martin, more recently Mr. Fisker has modified BMW and Mercedes-Benz luxury cars to create even more expensive custom cars that cost as much as $234,000. Tesla’s White Star is expected to cost between $65,000 and $70,000. The Fisker Karma, which is also planned for delivery in 2010, is expected to cost about $80,000.