This matter has to be interpreted in accordance with the Indian Contract Act. Let us examine this part by part:
Is an offer letter an offer or Intimation of Acceptance:
Fundamentally speaking, there are two documents - an offer letter and the appointment letter/joining letter. In the case of an offer letter, there is information about the salary or consideration along with an offer to join the company. However, in the case of an appointment letter, the stage of offer and acceptance is complete, and a final document is delivered. In the former case, there is an offer that you may or may not accept. In the latter case, you have a contract.
Things To Remember While Drafting A Valid Employment Contract
Contract = offer + acceptance
In the case of acquisitions positions of issued offer letters or appointment letters:
Any acquiring company takes the acquired company with all covenants attached. Therefore, all legal resources that are available against the acquired company are now available against the acquiring company unless specifically excluded in the acquisition documents. So, appointments issued before acquisitions are to be honored. However, the conditions are precarious when it comes to offers, as they are not yet contracts. Refer to the second paragraph of
Things To Remember While Drafting A Valid Employment Contract.
So, if the above issue is based on pure offers, then the new company can revoke them before acceptance.