The Wadden Sea risks losing its status as a world heritage site if the Netherlands continues to extract salt and gas off the north coast, Unesco has warned.

The organisation reiterated its concerns about the scale of the extraction, which it says is threatening biodiversity in the area, in the wake of a critical report by international environmental network IUCN.

Unesco has urged caretaker nature minister Christianne van der Wal to shelve plans to drill for gas at Ternaard. Ternaard is one of 175 small gas fields which NAM has a licence to exploit through pipelines beneath the seabed.

The government is currently phasing out gas extraction in Groningen because of the earthquakes and subsidence caused by the land settling after gas has been removed.

Economic affairs minister Stef Blok admitted at the time that mining activities could cause soil subsidence in the Wadden Sea.

Unesco said it feared for the loss of unique characteristics of the tidal site, which feeds nearly a million breeding and migratory birds. Noise pollution which can harm all marine species, is also a concern.

Van der Wal, who informed MPs of the report on Tuesday, has said she will defer comment until Unesco’s world heritage site committee decides what action to take at its next session in Ryadh in September.