Britney Spears in a November 2006 photo. Spears on Thursday explained why she furiously attacked a car with an umbrella -- she was rehearsing for a movie role. [Reuters]

When all else fails in Hollywood, blame it on "method acting." Pop star Britney Spears on Thursday explained why she furiously attacked a car with an umbrella -- she was rehearsing for a movie role.

As the former pop princess reinvents her career after a failed marriage, a stint in rehabilitation and panty-less pictures taken in public, Spears posted a note on her Web site, www.britneyspears.com, apologizing to the paparazzi for the umbrella-bashing incident, calling it a "stunt."

"I was preparing my character for a roll (sic) in a movie where the husband never plays his part so they switch places accidentally," the 25-year-old wrote. "I take all my rolls (sic) very seriously and got a little carried away."

"Unfortunately I didn't get the part," she added.

Method acting is a technique in which performers prepare for upcoming roles by immersing themselves in the real-life habits, experiences, emotions and thoughts of a character.

Back in February, the mother-of-two repeatedly struck a sport utility vehicle with an umbrella shortly before returning to a substance-abuse treatment center for the third time in a week, ultimately remaining in rehab for at least a month.

Her rehabilitation stint followed a spree of high-profile partying and other erratic behavior, such as shaving off her hair. Upon leaving in March she completed a divorce agreement with aspiring rapper and father of her sons, Kevin Federline.

Spears is trying to stage a comeback, performing for the first time in more than three years in May with a series of 15-minute shows at various nightclubs and reportedly working on her fifth album.