I am constrained to state that it would not be ethical or legal to suggest ways and means to deprive a workman of his statutory right to claim permanency in an industrial establishment when he is not at all disqualified to do so contextually.
Continuous Employment and Perennial Nature of Job
Firstly, the direct engagement of a workman as a casual laborer in an establishment continuously for a period of two consecutive years implies that the job on which he has been employed is certainly one of a perennial nature.
Entitlement to Continuous Service
Secondly, such continuous casual employment would automatically entitle him to earn the "continuous service" as defined under Section 25-B of the Industrial Disputes Act, 1947, for every year of service.
Unfair Labor Practice
Thirdly, as per item number 10 of Part I of Schedule V of the ID Act, 1947, employing any number of persons as badli, temporary, or casual on rolls continuously to deprive them of the status and benefits of permanent workmen is an unfair labor practice as defined under Section 25-T on the part of an employer and punishable under Section 25-U of the Act.
Therefore, if a trade union takes up the issue on behalf of such a long-serving casual laborer, your management could be in for much trouble. It is advisable to take steps to regularize such casual labor.