This paper proposes a novel direct load control method to stabilize the system frequency. The proposed method utilizes the consumers' controllable loads for load frequency control. By solving an optimization problem to maximize the social welfare function, the input required for the frequency control is allocated among the controllable loads and the load frequency control generator in an economically rational manner. To introduce the direct control program for smooth operation of the power system, preventing consumers from cheating and guaranteeing their benefits are required. Thus, strategy-proofness and individual rationality based on the Groves and Clarke mechanism were used to design the electricity charge. Each consumer bids on the utility functions truthfully to the independent system operator and gains from participating in the proposed direct load control program. The effectiveness of the proposed method was demonstrated through numerical simulations.