The authors measured net ionisation cross-sections of He, Ne and Ar atoms by 1.05 MeV amu-1 highly charged Heq+ (q=1, 2), Cq+ (q=2-6), Oq+ (q=2, 3, 5-8), Neq+ (q=2, 6=10) and Arq+ (q=4, 6, 10-14) ion impact using the parallel-plate condenser method. From these experimental results, they obtained projectile charge state, q, and effective charge, qeff, scaling laws for ionisation valid for a wide variety of the projectiles for each rare-gas target, and discussed them in connection with the classical trajectory Monte Carlo calculation of Olson (1979) with special emphasis on scaling laws. Generally, their results are in agreement with the calculations of Olson except for those of the Ne target, but the dependence of the cross-sections on the projectile charge state was found to deviate from the q2 law predicted by the calculation.