Citroen C4 'stop insufficient oil pressure'

am British living in spain, using my m-in law's citroen c4. as the car slows down (i.e. at traffic lights) the red stop light shows next to the speedometer screen, continuously beeps, and the screen, above the radio, flashes 'stop insufficient oil pressure', (in spanish, 'stop presión aceite insuficiente').
she has been to Citroen, they say its a manufacturers fault and they don't know how to fix it.
its annoying and would like to know if anybody has or has had the same problem and if it has been or can be fixed...