CDM 2015 defines the principal contractor as the contractor in overall charge of the construction phase. The principal contractor is normally a contractor so will also have contractor duties, however there should only be one principal contractor for a project at any one time.
A principal contractor (and a Principal Designer) is required to be appointed by the client on any project involving more than one contractor.
The principal contractor must be capable of carrying out the role and have the right skills, knowledge, training and experience. This will depend upon the nature of the work and the range and nature of health and safety risks involved.
The principal contractor is responsible for managing health and safety on the construction site, and must plan, manage, monitor and coordinate the construction phase so that health and safety risks are controlled.