"175. Principal contractor and sub-contractor deemed employers
(1) Where a person (in this section referred to as the principal) contracts with another person (in this section referred to as the contractor) for the execution of any work by or under the contractor and, in the execution of the work, a worker is employed by the contractor, both the principal and the contractor are, for the purposes of this Act, deemed to be employers of the worker so employed and are jointly and severally liable to pay any compensation which the contractor if he were the sole employer would be liable to pay under this Act.
(2) The principal is entitled to indemnity from the contractor for the principal's liability under this section.
(3) The principal is not liable under this section unless the work on which the worker is employed at the time of the occurrence of the disability is directly a part or process in the trade or business of the principal.
(4) Where the principal and the contractor are jointly and severally liable under this section, a judgment obtained against one is not a bar to proceedings against the other except to the extent that the judgment has been satisfied.
(5) Where compensation is claimed from or proceedings are taken against the principal, in the application of this Act a reference to the employer shall be read as a reference to the principal except where, for the purpose of calculating the amount of compensation, a reference is made to the earnings of a worker, the reference shall be read as a reference to the earnings of the worker under the contractor.
(6) For the purposes of this section, where sub-contracts are made