(1) Where any employer in the course of or for the purposes of his trade or business contracts with a contractor for the execution by or under the contractor of the whole or any part of any work which is ordinarily part of the trade or business of the employer, the employer shall be liable to pay to any employee employed in the execution of the work any compensation, which he would have been liable to pay if that employee had been immediately employed by him; and that the amount of compensation shall be calculated with reference to the wages of the employee under the employer by whom he is immediately employed.
(2) Where the employer is liable to pay compensation under this section, he shall be entitled to be indemnified by the contractor, or any other person from whom the employee could have recovered the compensation and where a contractor who is himself an employer is liable to pay compensation or to indemnify an employer under this section, he shall be entitled to be indemnified by any person standing to him in relation of a contractor from whom the employee could have recovered the compensation, and all questions as to the right to and the amount of any such indemnity shall, in default of agreement, be settled by the competent authority.
(3) Nothing in this section shall be construed as preventing an employee from recovering compensation referred to in sub-section (2) from the contractor instead of the employer.
(4) The provisions of this section shall not apply in any case where the accident occurred elsewhere than on, in or about the premises on which the employer has undertaken or usually undertakes, as the case may be, to execute the work or which are otherwise under his control or management.