The current–voltage characteristics of several manganite systems like La0.87MnO3–(Mn2O3)0.13, La0.60Y0.07Ca0.33MnO3 and Nd0.55Sm0.3375Sr0.1125MnO3 show non-Ohmic behaviour at different temperatures. The onset voltage V0(T) at which conductance starts deviating from its zero-bias value Σ0(T) scales as V0(T)∼Σ0(T)xT with x T being the onset exponent. A detailed scaling analysis with these manganite systems reveal that the onset exponents x T are different in the paramagnetic insulating and ferromagnetic metallic phases. Besides, the magnitudes of x T are different in different manganite systems. Non-Ohmic conduction and the onset exponent are described with the help of inelastic multi-step tunneling model and scaling concepts.