Explanation:

The basic purpose of a trade union is to prevent exploitation of workers.Under the doctrine of laissez-faire, in vogue during the 19th century, a worker was pitted against the management. Although he had the freedom to enter into a contract with the management, in practice, it had no meaning for the worker. The rule of hire and fire made the workers position even more precarious. A worker had neither the knowledge, nor the resources, to demand even legitimate dues from the management. As laissez-faire yielded place to the concept of a welfare state, trade unionism came to be recognised as a legitimate instrument for preventing explo-itation and promoting worker interest.