My Forrester break lights stay on when car is off
Did you push a button on top of the steering column? That button turns on the rear lights - it's a strange Subaru thing!
Check to see if your brake pedal is making contact with your the switch, it may need to be adjusted. If contact is made and the (brake) lights are still on, unplug the switch, if the lights go off after the switch is unplugged, replace the brake light switch
As FoR suggested, check the button on top of the steering column surround in front of your gauges. It's a regulatory requirement in the UK? for parking and is commonly asked. You can see what I mean here: http://www.cargurus.com/Cars/Discussion- c3468_ds577751#msg319118
It was the button
The button is also known as the virgin switch. Congratulations you are no longer a Subaru virgin!