1998 Ford Contour SE Pulling to the left HELP please!

I have a 98 contour that is pulling to the left ONLY when braking. (and by pulling...i mean it throws the whole car to the left and then shifts back right when you let off the brake.)
The front and back brakes have been changed (and are in the proper places)
All new front brake hoses, the brake fluid is coming out of them fine.
New wheel cylinders on the back.
The calipers have been rebuilt TWICE.
It does NOT pull at all when using the rear brakes (ie emergency brake)
When the car is 1st started it does not pull at all....After it is driven it starts to pull and gets worse the longer/farther it is driven.
The left rear tire is almost bald from it pulling so bad.
When I stop the front left wheel is the hottest of the two front if that matters.
PLEASE any ideas of what to check next will be VERY appreciated!!!
Thanks,
Bethany

Just an update this ended up being a bad bushing in the lower control arm.

thanks for the info. i have the same problem, but to the right when i brake. Time saver right here!