Experiments show that flux creep in HTSC at low temperatures is very sensitive to illumination. Thus, illumination as weak as few microwatts per cm^2 drastically accelerates the flux creep. It is important to underline that the effect exists in so different HTSC materials as Bi-2212 single crystals and YBCO films. We believe that the pair breaking process is responsible for this effect. This approach can explain experimental results qualitatively. In this case the sensitivity to illumination gives an important information about relaxation processes, which has to be very slow to explain the magnitude of the effect observed experimentally.