Coming down heavily on the practice of bureaucrats opting for temporary posting in public sector undertakings (PSUs), the government today said deputing officers, including those belonging to defence services, to state-owned companies was not permissible.It has, however, allowed government officials to join PSUs on immediate absorption basis.Railways would be the hardest hit by the directive as all the key posts in the PSUs under the ministry are manned by officers on deputation.The notification stresses that the directive would apply to all central PSUs including those under the ministry of railways."The practice of deputation was hampering development of managers in particular PSUs. The notification would address that situation," sources said.