Supporters of the old Kopu Bridge are outraged Thames-Coromandel's mayor wants to demolish it and turn the centre span into a land-based historical landmark.
Mayor Glenn Leach believes removing the 83-year-old bridge and creating a historical landmark site nearby is the best option for ratepayers, as keeping it fully functional could cost more than $100,000 a year.
It is no longer used for public traffic since the new $40 million two-lane bridge opened in December.
But his idea has been rejected by the New Zealand Historic Places Trust, which wants the category one protected bridge to stay, possibly incorporated into the national rail trail as a cycling and pedestrian bridge.
Trust mid-northern heritage adviser on architecture Robin Byron said turning part of the bridge into a land-based landmark would ruin its integrity because part of its value was in being an operational bridge.
"Our approach would be to refurbish the bridge because I think it has been neglected by the New Zealand Transport Agency for a long time.
"It is an important part of the heritage of the region and the bridge is of national significance. I think the council should reconsider this and make a commitment to keep it intact."
Thames resident Kim Buchanan is horrified that part of the town's history could be bowled.
Last year, she started a group, Save Kopu Bridge, to encourage the council to leave the swing span closed after the new bridge opened so it could be used by the public.
The Transport Agency had decided to leave the span open to allow boats to travel through it without anyone having to man it once contractors finished using it.
But after learning of the mayor's plans, Mrs Buchanan is collecting signatures urging the council to keep it as a functioning bridge. So far she has collected more than 500 but has not been allowed to place the petition at council-owned facilities including the iSite and the Thames library.
"I am so aghast - I still can't get my head around it. We believe because it is a historic place and the last remaining swing bridge in New Zealand that it needs to remain operational."
She said the opening of the swing bridge was also the main feature of a Thames heritage cruise. It was nationally significant because it had won an engineering award, it was the longest single-span bridge and the last remaining operational swing bridge in New Zealand.
Mrs Buchanan said demolishing the bridge would also come at a huge cost and was against the council's mandate to celebrate heritage.
However, Mayor Leach felt the best and more cost-effective option was a historical landmark - perhaps on a site near the bridge - with information about the history of the bridge as a way to celebrate the region's history.
"I think this is a good win-win solution to satisfy both the heritage advocates and those who want to keep rates low," he said.
Transport Agency state highway manager Kaye Clark said the agency was in early discussions with stakeholders including the Historic Places Trust, Thames Coromandel and Hauraki District Councils and Waikato Regional Council before making a final ruling on the bridge's future.
She said the cost and work involved in either transforming it into, say, a pedestrian and cycling bridge or relocating it would be a key consideration.