Dear Parag,
One of the meanings of the term " CASUAL " is occasional or irregular. When it is associated with the terms " work " and " worker " as an adjective, it denotes that the work is basically " on and off " or intermittent and thus not regular in nature as well as with a specific connotation to the person engaged on such a work as a purely temporary hand whose services are co-terminous with the occasional work. At times, a worker can be engaged on a regular or permanent work or perennial work for shorter duration also and there also he is called a temporary worker. Therefore, the casualness of such employment is determined by both the nature of the work and the duration of the employment of the worker on such work. So the mode of payment of wages and the statutory deductions if any made there of can not alter the basic character of such employment.
In the State of Tamil Nadu, there is a special enactment called " The Tamil Nadu Industrial Establishments ( Conferment of Permanent Status to Workmen ) Act,1981 " which mandates that every temporary workman completing 480 days of continuous service in an industrial establishment covered by the Act within a period of 24 calendar months should be made permanent.
Whether there is such a Law in your State or not, I would certainly like to point out further that the Industrial Disputes Act,1947 declares the practice of keeping workmen on temporary roll for years together so as to deprive them of the status and privileges of permanent workmen as an unfair labor practice on the part of the employers [ item no.10- Part I -Schedule-V ].
Therefore, it is better to make such casual workmen permanent in view of the length of their service as such and the perennial nature of the work in which they are engaged irrespective of its type being core or incidental.