Avril Lavigne is being sued by a 70s rock band over claims she copied one of their songs.Songwriters Tommy Dunbar and James Gangwer, members of The Rubinoos, allege Lavigne's hit 2007 single 'Girlfriend' is strikingly similar to their 1979song 'I Wanna Be Your Boyfriend'.Dunbar - who filed the lawsuit in San Francisco on July 2 - said: "We are not so naive as to chalk it up to some sort of cosmic coincidence."The lyric, the metre, the rhythm - they're identical."However, Lavigne's manager, Terry McBride, insists 'Girlfriend' has no resemblance to 'I Wanna Be Your Boyfriend'.He said: "The suit has no basis. There's nothing similar. Our musicologist says there are no similarities of melody, choral progression or metre."Despite saying the songs have no similarities, McBride says he would be prepared to settle the case out of court.He added: "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."Avril has insurance that covers these sort of suits that are so prevalent in this business."The case is due to be heard in California on August 28.