Peugeot 207cc Depollution System Faulty?

Hi
I have a Peugeot 207cc auto 57 plate. I have been told my peugeot has a Depollution system faulty error from my mechanic. When I drive it, it seems like the exhaust is blocked when pressing the accelerator it just does not want to go, after couple of seconds it will start to pick up speed. It is really sluggish. Could you please advise what I could do? Your help will be much appreciated.

Regards
Taz