RCA singer Avril Lavigne is being sued by two co-songwriters who claim that her hit "Girlfriend" sounds like a track their American power pop band recorded in the '70s.

Tommy Dunbar, founder of the Rubinoos, filed the suit in San Francisco's Northern Federal District Court on July 2.

The suit alleges that "Girlfriend" bears striking similarities to the Rubinoos' song "I Wanna Be Your Boyfriend," co-written by Dunbar and former Rubinoos' road manager James Gangwer, and released by Beserkley Records in 1978.

The lawsuit also names as defendants Lavigne's publishing company Avril Lavigne Publishing and the co-writer of "Girlfriend," producer/remixer name Lukasz Gottwald, also known as Dr. Luke, Doctor Luke, Luke Gottwald and Lukasz Gottwald.

Lavigne's Vancouver-based manager, Terry McBride, CEO of Nettwerk Music Group, claims the suit "has no basis."

"There's nothing similar (between the two songs)," he says. "Our musicologist says there is no similarities of melody, choral progression, or meter."

McBride, however, may settle the suit out of court if the costs of defending the case start to prove too high.

He says, "You are forced to consider doing this because American lawyers can do these cases on contingency. If I defend and win, it costs me $300,000. If I go to get my costs back, the other party declares bankruptcy. You end up footing the bill."

McBride adds, "Avril has insurance that covers off these sort of suits that are so prevalent in this business."

Sony BMG singer/songwriter Chantal Kreviazuk, also handled by McBride for management, took a swipe at Lavigne's songwriting chops to freelance writer Bob Cannon in the June issue of the U.S.-based magazine, Performing Songwriter.

Fellow Canadian Kreviazuk had co-written six songs at her Malibu house with Lavigne for the sophomore 2004 album "Under My Skin."

Dunbar and Jon Rubin formed the Rubinoos as middle school students in Berkeley, California in 1973. The band is best-known for its 1977 remake of the Tommy James and the Shondells' 1967 hit, "I Think We're Alone Now," which reached No. 45 on the Billboard Hot 100 chart.

The Rubinoos disbanded in 1985 but reunited in 1999. In 2007, Castle Communications in England issued the 63-song retrospective "Everything You Always Wanted to Know About the Rubinoos."