The New Zealand Historic Places Trust and former trust Otago area manager Bruce Albiston have urged the council's strategy committee to list all of the harbour as a heritage area.
The trust, in a letter to the council, said that in 2004-05 it recommended the council protect the harbour area, not just individual sites.
Mr Albiston told the committee this week that recommendation may have suffered from "corporate memory loss".
He urged the council to adopt the trust's recommendation, as required under the Historic Places Act.
"The harbour should be included [in the heritage list] in its own right, not just a list of items," he said.
A report to the committee by policy planner Richard Sutherland listed 14 important items at the harbour the council could consider listing in its district plan.
The items include buildings, objects, places and sites within the harbour area that are not listed for protection.
They range from Holmes Wharf and Normanby Wharf through to the "red sheds" and even a mast salvaged from the wreck of Robert and Betsy.
Railway lines, the Cape Wanbrow gun emplacements and the Oamaru lighthouse are other items.
But Cr Jim Hopkins said the issue was not so much what should be listed, but the cost of doing that.
A plan change could cost $100,000 to $150,000.
"If there are other cheaper ways to protect them, then those should be considered in the interests of ratepayers," he said.
Cr Peter Garvan said it had been 10 years since the heritage list had been added to and he believed the council should take a wider view, not just consider individual buildings or items.
Mr Sutherland outlined the process needed to prepare for listings, which the committee received.
The options were to initiate a plan change listing the 14 items in the district plan; to place the whole harbour area and Harbour-Tyne Sts historic area on the heritage items list; or expand any plan change to include other unlisted heritage items in the district.
If listed, any activity or development that affected a heritage item needed to be considered on its own merits and could be handled as a non-notified application - meaning no public submissions - with the written agreement of the New Zealand Historic Places Trust.
Without such agreement, it could be notified for public submissions.
