No employee's contribution shall be payable by or on behalf of an employee whose average daily wages 5-~[during a wage period are below 54[such wages as may be prescribed by the Central Government
Explanation.-The average daily wages of an employee shall be calculated (in such manner as may be prescribed by the Central Government

Contribution (both the employer's contribution and the employee's contribution) shall be payable by the principal employer for each [wage period] [in respect of the whole or part of which wages are payable to the employee and not otherwise.