Economic Development Minister Steven Joyce says the new super economic ministry will result in a faster decision and policy making process.
The Ministry of Business, Innovation and Employment formally starts on Monday after the merger of the Ministry of Economic Development, Department of Labour, Ministry of Science and Innovation and Department of Building and Housing.
Mr Joyce says he cannot yet predict the number of redundancies that will result as it will be months before the ministry is actually operating as a single agency.
The Public Service Association questions whether the new ministry is justified.
Secretary Richard Wagstaff says continuous restructuring in the public sector is coming at a cost.