Formula One's governing body has written to teams warning them any system that adjusts a car's suspension and ride height between qualifying and the race is illegal.
The move follows speculation some teams have been using devices or systems that give cars an aerodynamic advantage when qualifying light on fuel and then ensure the car has sufficient ground clearance when the tank is subsequently filled for the race distance.
McLaren suggested at the Australian Grand Prix last month that Red Bull, one-two winners in Malaysia last weekend, were using some sort of ride height control system.
Red Bull have denied the accusation and team boss Christian Horner they would protest any rival using such a system.
Active ride systems, pioneered by the original Lotus team and also used by Williams, have been banned under regulations since 1993.
