Vauxhall Zafira white smoke billowing out, no acceleration when pedal down cant do over 30 and spanner light on

reg wl52 lyo vaux zafaria 2.0 tdi elegance. had a problem about 9 months ago when the power went and couldnt accelerate and rev s were working.turned engine off and on and seemed to work.car has been off the road for 6 months due to an electrical problem.solved this and replaced battery.took car to sussex 700 miles and no problems.checked water oil etc as i do on all long journeys.couple days after getting back the car wouldnt accelerate and cruised at 30, no power when put foot down although revs went up.spanner light came on.today got in car to see the problem and after raveling 50 yards up a slight incline white smoke billowed out exhaust.couple people said might be exhaust filter or any type of filter.