The establishment of the centres spans three different governments - one Labor and the other two coalition.
"The Department of Immigration and Border Protection's management of procurement activity for garrison support and welfare services at the offshore processing centres in Naura and PNG (Manus Island) has fallen well short of effective procurement practice," the ANAO says in its report.
"This audit has identified serious and persistent deficiencies in three phases of procurement activity undertaken since 2012 to: establish the centres; consolidate contracts; and achieve savings through an open tender process.
"Of most concern is the department's management of processes for contract consolidation and open tender."
The Australian government had hoped to rein in growing expenses through this contract consolidation.
Sadly, this was not the case.
"In both cases the approach adopted by the department did not facilitate such an outcome," the ANAO report says.
"The department used approaches which reduced competitive pressure and significantly increased the price of services without the government authority to do so.
"The conduct and outcomes of the tender processes reviewed highlight procurement skill and capability gaps amongst departmental personnel at all levels."
The audit found that in engaging Transfield it set aside an earlier approach Serco.
However, the department did not require Transfield to say what services it would deliver and at what price. That made it hard for the department to show it had conducted a "robust value for money assessment".
The audit also found the Salvation Army was assessed as providing value for money on the basis of availability, without any specification of the services to be delivered or the price.
The department could not provide any records of how Save the Children was assessed as providing value for money.