Volkswagen Touran brake failure

last night whilst driving the car i had to brake a little sharpish and turn into a left turn at the same time when braking...then on the next touch of the brakes the pressure was gone...jarred on sharp stops the car but keeping the pressure on the pedal drops to its lowest point...you can pump it up again but again it loses the pressure...after stopping the car 10 mins later and pressing and depressing the pedal when stopped the pressure returned back to normal..is this the ABS at fault?.sensor fault?......the brakes feel ok now but its worrying to drive it against it happens again..any ideas guys!??