Dear friend,
As long as any activity in the establishment is not prohibited u/s 10 of the CLRA Act,1970, it is not illegal to do such work by engaging contract labor. But, apart from the ethical stand-point, changing the contractors from time to time while keeping the same set of contract labor on the same work belonging to the same principal employer's establishment continuously is not advisable on the following grounds:
1) Such a practice indicates that despite it being incidental,the outsourced activity is of perennial nature.
2)The change in the contractor after the expiry of every spell of the contract by retaining the same contract labor would indicate the fact that the contract is a sham one or just an umbrella contract.
3) The issue of payment of gratuity can become a contentious matter with the efflux of time.
4) Such a practice in the long run can lead to raising of industrial dispute for absorption of contract labor as regular workmen of the establishment.
When the statutory liabilities to provide same conditions of work to the contract labor on par with the regular workmen doing the same work and payment of minimum wages are enjoined upon the principal employer, why don't the management consider to do away with contract labor in respect of such perennial nature of work?