Is fashion an art?

It depends; on the designer, the label's style and the season.
There's no doubts about the John Galliano's fashion shows, for example. Artists/ Designs like him, Cavalli, Lagerfeld, McQueen always surprise us, mainly in the Couture fashion shows with embroidery and paints (probably mades manually, once we're talking about Couture) that bring our eyes tears.
There's controversies about pret-a-porter. We think about art as something more exclusive, i guess, single and when we face a lot of clothes that looks exactly the same we ask: Is this art? Maybe, kinda, everything should be connect to the context that's in.
The 2008 winter of Forum Tufi Duek bring a lot of dresses made by roses, a trully art. What you tell me about the Maria Bonita cardigãs in the same season? It's art in ready to wear, spreading its wings in the Rio and Sao Paolo fashion weeks.
From the modesty of the 'clean' looks that Francisco Costa makes to Calvin Klein to the violins of Viktor and Rolf, passing by Jum's paper, Vivienne Westwood's punk chic, and Cavalli's patch works, the fashion world is trying very hard to be recognized as an art.
Meanwhile, for us just left admire and try to wright our own story in this art called fashion.