A reclusive millionaire is facing calls to down tools on his 20-year hunt for billions of dollars worth of buried gold on Robinson Crusoe Island over fears the search will devastate the Unesco protected site.

Bernard Keiser, a Dutch American millionaire based in Chicago, has since 1998 been digging on the remote Chilean island for mythical lost treasure, worth an estimated $10 billion.

The protected nature of the island means his team have only been allowed to use simple, manual tools such as shovels, brushes, and knives so far. Blasting and more traditional mining techniques have been severely limited – until now.

On September 2 the Chilean authorities approved Mr Keiser’s request to use diggers on the island, a Unesco World Biosphere Reserve.

But this week, a Chilean politician filed an emergency petition to block the dig.