Citing concerns about potential traffic and overdevelopment, the Los Angeles City Council ended a bitter years-long battle over the controversial Las Lomas mini-city Wednesday and voted to kill the entire proposed 5,553-home project.

In its 10-5 decision, the council ordered the Planning Department to stop processing Las Lomas' annexation and development applications and return all studies and paperwork to the company.

The decision comes after six years of work and a $20 million investment by developer Dan S. Palmer Jr., who sought to build a 555-acre self-contained community of homes, offices and shops on the last stretch of open space between the city of Los Angeles and Santa Clarita.

But council members said they did not even want to consider expanding Los Angeles' city limits to include such a large project in the already traffic-clogged Newhall Pass.

"This was critically important at this moment in time in the city of L.A. that we just say no. We can't afford overdevelopment and this is overdevelopment," said Councilman Greig Smith, who led the effort to block the project.

"This project would have put 15,000 cars per day in an already impacted area. The people of L.A. said we can't take any more. We're tired of it. We don't have to say yes to make a developer rich."

But several council members and the City Attorney's Office warned that the decision could expose the city to a potentially risky and expensive lawsuit from the developer.