Renault clio key/immobiliser not working?

My wife's clio car key is working in terms of when you press it the red light on the key flashes. However the car does not open/lock at all. The car will not start at all with the key in the ignition (the engine will not turn over)and none of the electrics will come on e.g. lights, radio. In essence its as though the car has died. The key started playing up a few weeks back e.g. not working for several attempts and then suddenly working. Any ideas of how to resolve this issue would be very much appreciated. Its a 2001, 1.2 grande