You can review the following draft:
To
Mr.............
...............
Dear Sir,
Subject: Campus Selection
Please refer to our letter dated ............. offering you the position of .................. in our company. We would have cherished your association with our company as we believed that you have the potential to contribute to the growth of the company. However, we are pained to inform you that we are constrained to withdraw our offer due to .......(explain the reasons).......
We will not hesitate to be in touch with you when the constraints are over. In the meantime, we thank you for your response to the campus interview and wish you a bright career ahead.
Yours sincerely,
Competent Authority
Note: This offer letter can be modified by you to suit your circumstances.
Regards,
B. Saikumar
HR & Labour Law Consultant
Chipinbiz Consultancy Pvt. Ltd
Mumbai
Tel: [Phone Number Removed For Privacy Reasons]