LOS ANGELES — July is shaping up to be the cruelest month for Avril Lavigne.

Over the past two weeks, the pop princess' carefully crafted image as the anti-Britney — that is, a chart-topping ingenue who writes her own songs, spits at paparazzi and has shaped her own spiky-yet-vulnerable image — has come under attack on multiple fronts.

In a lawsuit made public last week, the 22-year-old Canadian artist is being sued for copyright infringement for allegedly plagiarizing a substantial part of "I Wanna Be Your Boyfriend," a song by '70s new-wave group The Rubinoos, for her worldwide smash hit "Girlfriend."

As with most Information Age disputes, the controversy has spilled over onto www.YouTube.com, where various video clips highlighting similarities between the two songs — specifically, their sing-song-y, call-and-response choruses of "Hey, hey/You, you" — have been streamed more than 1.4 million times since July 4.

Now, speaking publicly on the matter for the first time, "Girlfriend's" co-writer Lukasz "Dr. Luke" Gottwald has lashed out at the plaintiffs — songwriters James Gangwer and original Rubinoos member Tommy Dunbar — denying allegations that he and Lavigne "copied" "Boyfriend."

"I never heard of The Rubinoos before the lawsuit," said Gottwald, who has crafted hits for Kelly Clarkson, Pink and Daughtry, among others. "I never heard of the song, and neither has Avril. I would take a polygraph on that in front of them."

Gottwald said he and Lavigne wrote the song together.

"It started out with Avril wanting to make something fun and upbeat," he said. "It has the same chord progressions as 10 different blink-182 songs, the standard changes you'd find in a Sum 41 song. It's the Sex Pistols, not The Rubinoos."

The lead singer of The Rubinoos, Jon Rubin (who is not a part of the lawsuit because he didn't write it), said that in terms of meter and chord progression, "Girlfriend" bears a close resemblance to "I Wanna Be Your Boyfriend." He also thinks that "Girlfriend" has more similarities to a 1997 cover version of the song, retitled "I Wanna Be Your Girlfriend" by the female-fronted Brit-pop band Lush. Rubin said: "We got tons of e-mails about it. 'You guys must be collecting big dough now.' Well, actually not."

"Girlfriend" has sold 2.6 million copies worldwide and topped singles charts in the U.S., Italy, New Zealand, Austria, Ireland and Sweden. Lavigne was unreachable for comment, her manager said, but defended herself Friday on her MySpace page:

"Off the top of my head, two other songs that I can immediately think of with this type of lyric are 'Hey, hey, you, you get off of my cloud' by the Rolling Stones and 'Hey little girl I want to be your boyfriend' by the Ramones," the singer writes. "Simply put, I have been falsely accused of ripping their song off. Luke and I have done nothing wrong and there is no claim to their part."

The plaintiffs and defendants hired musicologists to prepare reports on "Girlfriend's" and "Boyfriend's" respective similarities and dissimilarities.

Not surprisingly, Dunbar and Gangwer's musicologist found "an unusually high degree of similarity between the songs," said Nicholas Carlin, a lawyer for songwriters Dunbar and Gangwer. A report by musicologist Anthony Ricigliano, commissioned by Lavigne's management, states: "Although these compositions contain similar material, they do not share any significant similarity in lyric content, melodic content (pitch series, rhythm or rhythmic patterns, melodic development or structure) or harmonic content, to suggest that 'Girlfriend' was copied from 'Boyfriend.' "