In photoluminescence kinetics of the InP quantum dots, we have found a long-lived component of the degree of circular polarization, showing practically no decay during the lifetime of excitation. It is shown that this effect is observed only in the charged quantum dots. The amplitude of the long-lived PL polarization can be controlled by an applied electric field and may be as high as 50% in the case of quasi resonance excitation. The existence of the long-lived component of the polarization is the clear evidence of large lifetime of the electron spin polarization in quantum dots.