Am I entitled to a refund by my tailor?

I bought a new dress which was slightly too long. Took it to the tailor for a simple hem alteration-shortening. When I picked it up, the back was 3 inches shorter than the front. He�s since tried to fix it - twice, once by undoing the whole dress and putting it back together, but every time he tries it looks worse. The dress is way too short and now unwearable. I took the dress, brand new, with tags on. I am asking him for a refund of the repair cost AND the cost of the dress, since I need to buy a new one for the event I bought it for. He has so far refused to refund me anything and is adamant on trying to fix it. Please advice??!!! Is there any "legal" guidance, any citizens body or any etiquette I an refer to?