An integrated guidance and attitude control scheme for asteroid proximity operations is presented. The development of this algorithm is motivated by the desire to implement robust and integrated spacecraft GNC schemes for asteroid close proximity operations. Autonomous maneuvering about small bodies is particularly challenging because of the uncertain, low-gravity environment. Based on Higher Order Sliding Mode (HOSM) control theory, the integrated Multiple Sliding Surface Guidance and Control (MSSGC) law has been designed to drive the system to the selected sliding surface in a finite time. The MSSGC scheme integrates the spacecraft's guidance and attitude control into a common framework that guides the 6-DOF spacecraft to a desired position about the asteroid with the desired orientation, all without the need for a pre-computed reference trajectory. A Lyapunov-based stability analysis shows that the system is globally stable against unmodeled dynamics and perturbations typically expected in small body environments. Results demonstrate that the algorithm is successful in driving the system to the desired target point (either landing on the surface or hovering above a desired location) with zero velocity and with the desired attitude and zero rotational rates.