Dealer lied about accident history

AFTER searching for weeks, I found a 2007 Ford Mondeo XR5, which was advertised as brand new. The deal I was offered was so good that I asked the salesman if it had ever been in an accident or hail damaged. I was told it had not. On the way home I could hear wind gushing through the door sills and, on inspection, the paint on the driver's side door and passenger door looked different. The gaps in the doors were different and I noticed overspray. I phoned the dealer and was eventually told it had been in an accident. I demanded the deal be called off, but he said the car was registered in my name and it was too bad. They offered to repair it, but I feel so ripped off. Ford said they couldn't do anything; it is the way the franchise has treated me, so they are powerless.