The former State Services Minister who oversaw the re-shaping of the public service in the 1980s, Stan Rodger, says the only restructuring worth doing is big and bold.
Prime Minister John Key is set to announce details of the next wave of changes to the public service in a speech on Thursday afternoon.
Mr Key has signalled some mergers, but says there will not be wholesale restructuring.
Mr Rodger, who was minister when tens of thousands of workers were transferred from government departments to state-owned enterprises, says small changes can be costly and ineffective.
He says the only way to make significant savings is to look at the functions the Government is undertaking, and remove any that are no longer relevant.
However Labour MP says he is no longer convinced that major restructuring of the public service delivers results.
Mr Mallard was State Services minister from 1999 until 2005.
He says proper change can take three or four years to bed down, during which time agencies can be distracted from their core role.