It was a whirlwind friendship that began in the summer of 2003 between two of Canada's more notable singers. Chantal Kreviazuk and Avril Lavigne had a lot in common from the start: they both left their hometowns to launch careers in Toronto; they each have a contract with Ford models; both are represented by the same management company; the women have appeared in minor film roles; and both are now married to Canadian rock royalty (Kreviazuk to Our Lady Peace's Raine Maida and Lavigne to Sum 41's Deryck Whibley).

"Sometimes she was my muse," Kreviazuk told Rolling Stone in 2004. "We became really good friends," added Lavigne. "Every single night for two weeks, we would write a new song."

The pair accomplished quite a bit during a time that found Lavigne temporarily moving into Kreviazuk's home with Maida to write, ultimately penning six songs together that would appear on Lavigne's previous smash album Under My Skin. Maida, who has also written and produced tracks for Kelly Clarkson's Breakaway album, also produced five of the album's songs.

Now, however, it seems like the relationship has soured, which was confirmed by Kreviazuk in the June issue of Performing Songwriter. When interviewer Bob Cannon brought-up having just done a piece on Lavigne, Kreviazuk interrupted:

I find it funny that it's in Performing Songwriter. I mean, Avril, songwriter? Avril doesn't really sit and write songs by herself or anything. Avril will also cross the ethical line, and no one says anything. That's why I'll never work with her again. I sent her a song two years ago called "Contagious," and I just saw the track listing to this album [the newly-released The Best Damn Thing] and there's a song called "Contagious" on it—and my name's not on it. What do you do with that?

Rrowr! Though Lavigne is enjoying unprecedented success with her latest number one album and single ("Girlfriend"), the rocker from Napanee hasn't been ingratiating herself to many lately. In September, Lavigne spat in a photographer's face outside Hyde nightclub in Los Angeles and was videotaped spewing profanity toward autograph seekers. She didn't do herself any favours during a bizarre television interview, and "Gossip Gangster" Perez Hilton has made an effort to keep her square in his sights, telling Vice that he'd like to ruin her career and calling Lavigne a "fucking douche" before introducing Kreviazuk at an L.A. show. Critics have also pointed out the similarities between Lavigne's "Girlfriend" and the track "I Wanna Be Your Boyfriend" by The Rubinoos (you be the judge).

Lavigne collaborator Evan Taubenfeld, now fronting L.A.'s Black List Club, answered the controversy on the band's website. "'Contagious' on Avril’s [album] was written solely by Avril and myself," Taubenfeld states. "In fact, we originally wrote it for me, so there’s no way Chantal was involved."

Kreviazuk admits that the songwriting collaborations have been personally satisfying, however. "It's selfless, and there's a lot of sacrifice in that," she also tells the magazine. When asked if she's placing a call to her lawyer to check into "Contagious," Kreviazuk replies, "See, I won't do that. I'll just tell you. Art should not be subject to that kind of controversy."

UPDATE: Whoah—a lot has happened since this story broke...

• Lavigne released a statement via her website, saying, "Chantal's comments are damaging to my reputation and a clear defamation of my character and I am considering taking legal action. My decision to discontinue working with Chantal after co-writing together on my second record was simply based on the fact that we had no hits together. That is why her name is not on this record, despite her numerous attempts to be included, which were always denied. From my perspective, this is a clear case of bitterness." Lavigne also admitted that Kreviazuk did email her with an apology following the publication of the magazine article.

• Via an official statement from her management company, Nettwerk, Kreviazuk has retracted the statements: "When I heard [the song], I immediately realized it was a coincidence. The songs have nothing in common...my statements and any inference from my statements, which call into question Avril's ethics or ability as a respected and acclaimed songwriter, should be disregarded and are retracted. Avril is an accomplished songwriter and it has been my privilege to work with her."

• Lavigne now faces a lawsuit from Rubinoos founder Tommy Dunbar, who alleges that "Girlfriend" plagiarizes "I Wanna Be Your Boyfriend," which was released in 1978. Lavigne claims that she has neither heard of the song or the group, and pointed out similar elements in other songs. The Rubinoos are best known for their 1977 cover of "I Think We're Alone Now," originally by Tommy James and the Shondells.

• In an additional setback, a new accusation has come to light that Lavigne's song "I Don't Have To Try" bears striking similarities to "I'm The Kinda" by Canadian artist Peaches (listen to the two song clips here). This accusation comes with some uncomfortable timing—Lavigne told InStyle magazine this month that the Peaches track is one of her top five favourites.