The Public Service Association says there is a growing trend for the Government to bypass the public service for advice.
A private sector advisory board has been appointed to help Treasury develop a 20-year national infrastructure plan.
The Government is already using senior private sector people as ministerial purchasing advisors and for the Auckland super-city transition agency.
Public Service Association national secretary Brenda Pilott, says there is clearly a problem between the Government and the public service.
"They don't appear to trust or be able to rely on the advice they get from the public service, and I think that should be a very grave concern to senior people in the public service, and indeed to ministers," she says.
Ms Pilott says money spent on consultants should be used to build up the expertise of the public service.