NSW Do I Have a Case Against the Council for Negligence?

Hi, do I have a case against the council for negligence? Surely there must be a duty of care. I would appreciate any assistance on the following issue.

I was an owner builder but hired a qualified builder and tradespeople to help built a set of dual occupancy units, which were passed by council and a final certificate was issued in 2007, stating all things were built as per the engineers drawings, etc.

In 2012, I finalised the subdivision and a strata plan was created. Once again the council signed off that everything was built according to the engineers drawings.

In August 2015, I went to sell my property only to find from an engineering report that there was negligence on the council and/or builder and that the work is non-complying. Significant structural retaining walls under the house were not constructed as per the engineering drawings.

8 years have passed and the builder has retired. There must have been several inspections / hold points for sign off by council inspectors in regards to footings and retaining walls underneath the house. The cost to rectify this work is $78000.

If this had of been picked up by the council after the footings were poured and before the walls were built the cost to comply would have only been a fraction of this cost.

Can anybody help?