My 206 brake lights never go off, help??

Ive recently bought a 206, i noticed the other day that my brake lights would be on even if i wasnt applying any pressure to the pad, the only way for me to stop it is to put my foot uder the pedal and pull up but i cannot do this when driving... ive ust had new pads and disks put on the car and the problem persists, can any one help??
Thanks