A top-level summit was last night deciding whether plans for a supermarket and homes development at Hayle Harbour would affect the area's coveted World Heritage site status.
Cornish Mining World Heritage Site co-ordinator Deborah Boden said she believed fears that the town's South Quay scheme might have an adverse effect on its international standing as a place of unique historical importance were largely unfounded.
Mrs Boden, who heads a small team based in Truro, was responding to reports that the United Nations Educational, Scientific and Cultural Organisation (Unesco) – which oversees World Heritage sites throughout the globe – would be discussing the issue at a meeting in Cambodia last night.
Unesco's advisory bodies have urged the committee to "consider placing the property on the list of World Heritage in danger" if the project to build an Asda store, 30 houses, a restaurant and shops goes ahead.
"In theory they could say Hayle Harbour has been negatively impacted and decide to remove the status from the whole of the site," said Mrs Boden.
"But I doubt they would do that. It's only a small part of the much wider 20,000-hectare World Heritage site across Cornwall and West Devon."
Dutch firm ING has been granted planning permission to develop the harbour, which has been derelict for 30 years. The company is currently in negotiations with Asda about building a supermarket which would create up to 270 full-time and part-time jobs. Cornwall Council has stated that money generated from the development would be used to improve the harbour.
The authority's head of planning, Phil Mason, said: "The really important thing is the community of Hayle."
However, heritage and conservation groups argue that the West Cornwall port is a key part of the Unesco World Heritage site because of its foundry and quay, from where metals and revolutionary engineering equipment were shipped to the world.
Last year the Department of Culture, Media and Sport refused a request from English Heritage to formally call in the planning decision.
A spokesman for English Heritage said: "We regret that the Secretary of State decided not to call in the application for development on the South Quay at Hayle. We believe the effect on the Cornwall and West Devon Mining World Heritage site is such that it affects the UK's national obligations to the Unesco World Heritage Convention, which we believe justifies consideration of the scheme at a national level."
The 37th session of the World Heritage Committee opened in Phnom Penh on Sunday and will last for ten days and involve some 1,400 delegates from 121 countries.
As well as reviewing the status of existing sites – such as Cornwall and West Devon – the committee will rule on the inscription of new sites.
A decision on the Hayle issue is expected to released today.