renault laguna 2003 dci wont start. how to fix it ?

hi I have a 2003 Renault laguna 2. 1.9 dci the car cut out and will not start again. it was running fine until this point it will turn over but wont fire and there is a warning light flashing (red light that shows a picture of an engine) I can get the car to run on easy start but as soon as I withdraw this it stops again. can any one help? many thanks lee