Is there any legal obligation to take old contract employees on same term & condition with new contractor?

Dear Senior ,
Please suggest that if the principle employer has changed contractor. A new contractor is hired for doing same work through tender process as has quoted less price for doing the same work. The total no. of employees working under contractor is more than 600nos. & they ( contract worker of old contractor ) have a recognized labour union. The union is saying to absorb old employees with new contractor .Is there any legal obligation to take old contract employees on same term & condition with new contractor.
Regds/Ashe

No;the new contractor engaged by the Principal Employer in the same work has no legal obligation to take the contract labor of the previous contractor. When the previous contractor could not provide employment to the contract labor engaged by him so far due to non-renewal of the contract, it can not be treated as retrenchment also.