Active safety control is significant for ensuring the safety of both passengers and vehicles, and has been developed into various independent systems, such as anti-lock braking system, electronic stability programme system, steering by wire system, etc. However, with these independent systems, the control targets could intervene with each other. As a feasible strategy, the coordinated control, also namely the bottom-to-top control scheme, can improve the overall vehicle performance to some extent, but the performance compromises among independent controllers and the redundancies of sensor harness limit their full function display. In order to reach the maximum performance improvement, the top-to-bottom integrated motion control scheme for 4-wheel-independent vehicles considering critical conditions is developed in this paper, that is, the vehicle motion is controlled with a virtual control input on a top level, and then, the virtual control input is optimally allocated to and implemented by each wheel at the bottom level. The complicated allocation problem is handled via choosing proper allocation variables and corresponding allocation constraints, and meanwhile, the critical working conditions that could be created by emergency obstacle avoidance, cornering braking manoeuvre, etc., are considered to guarantee the vehicle stability. The effectiveness of the proposed controller is verified via simulations with different driving conditions.