As engineering systems become more complex, the need for ’optimal’ designs becomes apparent and very important. A centralised approach can be economically unfeasible, owing to computer limitations, or because it is too complex and cumbersome to be implemented. In this paper, an approach using a suboptimal controller is proposed leading to a structural optimisation problem of large scale systems (LSS). The mathematical formulation of this problem is provided. A new structural controller is developed, and a step-by-step algorithm to design it is provided. An overall cost is defined and can be computed from the proposed algorithm. Two simple examples illustrating the applicability and usefulness of the new structural optimisation approach are included.