Payment Made by Govt Dept to one time supplier - Supplier not paid GST and not filed return

In case a govt department has made payment to a one time supplier after deduction of TDS under GST. However it has come to the notice of the department that the one time supplier has neither paid GST nor filed his GST Return in the subsequent month. Under the circumstances what is the liability of the Govt. Department under GST and what should be the course of action since he has no control over a one time supplier. Please guide.