The label says I do, but I have lots of clothes from the same place (Jigsaw) that say the same, like jumpers and dresses, and when I've handwashed them they have been fine. I don't know if maybe they just say that to cover themselves sometimes as a retailer, against shrunken items being returned.
Not sure about silk though, does anyone know? It also says 'due to crinkle nature of the fabric we recommend you do not iron' - so dry cleaning seems a real waste anyway if it can't even be pressed. 
Thanks.