  The colossal electroresistance in manganites is a concomitant of the electric
field induced insulator-to-metal phase transition. A phenomenological phase
transition model is proposed to study this electric field induced collapse of
charge-ordered phase. The hysteresis of the phase transition is well explained
using the effective medium approximation. The volume fraction of metallic
region at the metal-to-insulator transition point is estimated as 30%. In
addition, it is found that the critical electric field to melt the
charge-ordered phase will decrease with the applied magnetic field.
