Construction of a double-storey house owned by Public Service Commissioner Andrew Kefford in Gawler Crescent, Deakin, was one of seven considered in the report that was prompted by complaints from nearby residents and subsequent media reports.

Auditor-General Maxine Cooper found major weaknesses in the work of some private building certifiers and said two of the seven homes considered should not have been approved.

Mr Kefford's house was built without a development application because it was approved by a certifier as being exempt from requirements.

A Certificate of Occupancy was issued by the Environment and Sustainable Development Directorate in November 2012 but complaints by neighbours resulted in an investigation being launched in February 2013.

The owners were required to lodge a retrospective development application after a second-storey balcony was found to be too close to a side setback and overlooking a neighbouring block.

Other issues, including landscaping, solar access and potential trip hazzards, were identified.

Development approval was granted in September 2013.

Monday's report found mistakes by the certifier related to boundaries meant the application was assessed as being exempt "when it should not have been”.

An investigation into the certifier's actions was ongoing and directorate officers were considering disciplinary action.

Dr Cooper recommended closer controls, saying monitoring of certifiers was inadequate.

She also recommended changes to the way planning applications were handled and complaints were monitored by directorate officers.

Dr Cooper said, in two cases, certifiers had incorrectly assessed developments as exempt.

In three cases, the certifier was being investigated, with “varying levels of disciplinary action” taken by the department. She also recommended a review of penalties for certifiers, which she said were small, with a maximum fine of $8400.

She investigated seven cases, including the Deakin house referred by the head of the public service after claims of improper influence, and a second case also raised in the media.

In the other five cases, a development application was lodged only after the houses were built, indicating the cases had been exempted from a development application but later found to need one.

In the case of the Deakin house and three other cases, the audit report found no evidence of improper influence, but a lack of documentation: “Transparency of assessing officers’ consideration of the application, which is a safeguard against improper influence, was compromised due to a lack of assessment documentation.”

A new house in O’Connor was found not to comply with the original plans.

A second two-storey house in Deakin, with a swimming pool and gazebo, and involving the removal of a regulated tree also had not been properly monitored and did not comply with initial plans.

Another case involved a house, tennis court and swimming pool in O’Malley, which was not consistent with the building code because it had a loft, making it three storeys, it did not have the required setbacks from the boundaries and it did not have required plantings. It should have been refused, the audit found.

While the wrong decision had been made, there was no evidence of improper influence, although, again, there was a lack of transparency and documentation.

A sixth case involved a house in Forde, which also didn’t comply. It was not within the maximum plot ratio, did not achieve required sunlight, was not set back the required distances and did not have the required open space. This one, too, should have been refused.

The directorate acknowledged the errors, which it said had occurred because the house was part of an estate development.

The seventh case was a house in Harrison that did not have required open space and was exempted by the certifier when it should not have been.

Dr Cooper pointed to a 2012 survey of 67 building surveyors who said they had lost business because they had refused to approve applications.

A senior member of the Environment and Sustainable Development directorate suggested “potentially improper” relationships between builders and certifiers, a view that three building inspectors shared.

The directorate had identified four certifiers who “require additional management”.

Dr Cooper also referred to a briefing to Sustainable Development Minister Simon Corbell in January that noted a sharp rise in the number of complaints about multi-unit buildings.

Of the 12 examples given, five related to one certification firm, and three of those to one certifier, the same individual involved in the Harrison home wrongly exempted.

The certifier was being monitored, the report said.

Dr Cooper recommended better training for certifiers, and a requirement for them to supply better documentation.

Mr Corbell welcomed the report's findings and said the government agreed with all its recommendations.

Directorate staff had been given instructions to implement changes immediately.