What does anti-pollution fault light mean?

hi just recently had major problems with my 307 Hdi. driving along the motorway when the anti-pollution fault came on. The car began to become more sluggish, then the car lost all power and the engine cut out. Luckily was near a hard shoulder. Turned the engine off and restarted the car and off I went again. It took a very long time to reach 70mph (well over 1 min) then boom the power cut out again. It done this 9 times in total. can anyone shed some light into what the problem is?