Why wont my Renault Scenic 1.4 16v Dynamique start?

My Renault Scenic has developed an electrical fault. Power from the battery is getting through but the car will not start. The problem is, if I attach jumpleads to the battery itself nothing happens, however when I attach them to the red housing attached to the the top of the baterry the car will start. Unfortunately as soon as I take the lead off the engine stops and will not start again

Simon Hickey
February 2008