You'd have had your answer by now if you'd tried a Google search for yourself.
Here are some ofthe answers you'd have found:
http://www.diynot.com/diy/threads/brake-lights-constantly-on-peugeot-206.43025/
http://www.peugeotforums.com/forums/206-35/brake-lights-staying-5586/
Anon
March 2016