Wine producers are furious about government plans to build a high-speed TGV train line – connecting the city of Bordeaux with Dax – that would run through the Ciron valley, near to where the famous sweet wines Sauternes and Barsac are produced.

Plans for the new €9 billion line include a huge points section of rails right at the heart of the valley's special ecosystem, credited with providing around 170 vineyard owners the unique microclimate that allows them to make the famous Sauternes vintages, including the famous Château de Y'quem  which can sell for hundreds of euros a bottle.

The project would see around 4,800 acres of forest and farmland destroyed.

Wine makers argue the line will blow away the uniquely humid microclimate and in particular a morning mist that is needed to make Sauternes.

'It will be a death sentence for some of the vintages that have been around for centuries," wine makers said in a statement to French media.

Philippe Dejean, president of the Union des Grands Vins Liquoreux de Bordeaux, issued a call to arms.

"We call on all who love sweet wines to make their anger known," he said.

Xavier Planty, the president of an organisation protecting wine makers interests, said the TGV trains would ruin the vital morning mist in the valley which is credited as being the secret to the success of the wines.

He says that would mean winemakers in the valley would not qualify for the all-important AOC government certification which is handed out to certain region-specific agricultural products with specific qualities and ingredients, like Champagne in north-east France.

According to local wine makers, the grapes used in making Sauternes wine owe their unique taste to the necrotrophic fungus (botrytis bunch rot) that lives on the vines and which is created by the mist that develops on the Ciron river and warms up by the time it reaches the Sauternes plains.

“If the water in the Ciron is warmed up, it is more difficult for the mist to form. We can't take the risk to mess it all up,” Planty warned.

The train line project, orchestrated by France’s national rail way network owner Réseau Ferré de France (RFF), still has to get a final green light from the government before it can go ahead. But despite this, Planty said the region’s wine makers are already planning on taking the project to the European Court of Justice.

Producers say 2,000 jobs in the industry are on the line as well as the revenue from the 200,000 wine tourists who visit the Sauternes area each year.

The train line is scheduled for 2027.