ABSTRACTA generalised scaling relationship of the imaginary part of the dielectric permittivity as well as of the real part of the dielectric permittivity is presented. The proposed scaling of the dielectric response has been successfully applied to main relaxation processes in various supercooled isotropic liquid phases and supercooled plastic-crystal phases in several glass-forming liquids as glycerol, propylene carbonate, 3-fluoroaniline, ethanol, cyclooctanol and cyanocyclohexane. Existence of the excess wing, the resolved secondary relaxation (β-relaxation) or both the processes was identified for some of these materials. It is demonstrated that behaviour of the resolved β-relaxation and the excess wing strictly depends on the parameters of the main relaxation process. This implies that the main relaxation process and the secondary one are not independent.