Catalysis of the reaction: UDP-N-acetyl-alpha-D-glucosamine + ditrans,octacis-undecaprenyl phosphate = UMP + N-acetyl-alpha-D-glucosaminyldiphospho-ditrans,octacis-undecaprenol.
UDP-GlcNAc:undecaprenyl-phosphate GlcNAc-1-phosphate transferase activity