General Motors received more clean energy patents in the past year than any other company, a study released Friday said.

GM's 135 patents represented nearly 14 percent of the 1,881 US patents obtained by 700 organizations in 2010, according to an analysis by the Clean Energy Patent Growth Index.

The successful patent applications came as GM made major investments in research and development despite years of intense restructuring and a 2009 government-backed bankruptcy filing.

"US clean energy patents were at an all-time high in 2010," said Victor Cardona, co-chairman of the Cleantech Group at the Albany, New York law firm of Heslin Rothenberg Farley & Mesiti, which specializes in intellectual property and published the index.

"GM has clearly put forth a lot of effort in a range of clean-energy technologies, resulting in its appearance at the top of the list for the first time."

Company officials said GM's patents covered hybrid electric vehicles, fuel cells and solar energy, with a focus on improvements to current and future technologies.

"GM is on a journey to reinvent the automotive DNA, and that's driving a great amount of innovation and technological breakthroughs," said Alan Taub, GM vice president of global research and development.

"We will continue our aggressive focus on advanced propulsion technologies that will benefit our customers and the environment."

GM received a total of 940 US patents in 2010, placing it in the top 25 of all companies. This includes sectors such as information technology and consumer electronics.

The Clean Energy Patent Growth Index tracks the granting of US patents in hybrid and electric vehicles, fuel cells, solar, wind and geothermal energy, biofuels and other forms of clean renewable energy.