406 HDI 11 stalls when brake is pressed please help!

[Strikey30]

Hi guys. I have a problem with my 2000 406hdi 110 estate. Every time I press the brake pedal the car stops. I initally thought it was when i pressed the clutch down as it stopped when i came up to junctions but its the brake pedal. I have stuck my head under the brake set up and there is two switches, one is white and the other one is black. I have found that when the brake pedal is applied the switched is released and the engine stalls right away. I have taken the switch out from its bracket and held it down with my thumb and the car runs ok and I can press the brake and it doesnt stall, but if I let the black switch go from my finger it stops. Can anyone tell me what the black switch behind the pedal does? Im guessing the white switch is for the lights? and the black one goes to the ecu or something? any ideas what might be wrong? Im wondering if I tape the switch shut will this get me by for a few days?

Thanks guys.