(Decanter) - Tensions are running high in the Rhone Valley with negociants and cooperative cellars clashing over the advance purchase of grapes for the 2014 harvest.

A letter was sent in early July to all cooperative cellars in the region, signed by the Cotes du Rhone winemakers’ union, to warn of ‘manoeuvres from certain negociants to assure their grape sourcing’.

The letter said some negociants were ‘resorting to underhand tactics and potentially cutting off supply to cooperative cellars’. It also reminded cooperative members that they face fines and possible exclusion if they send their grapes elsewhere.

The move has revealed rising tension in the region over grape supplies.

Harvest volumes have dropped in the Cotes du Rhone over the past decade, due to grubbed up vines and difficult weather. The grape crush from 2013 was particularly low, at 1.2m hectolitres. The overall Rhone Valley harvest was 2.5m hectolitres, down 13% on 2012.

‘We are particularly concerned by this as we work with so many growers,’ said Serge Roux, president at the Rhone’s largest cooperative company, Le Cellier des Dauphins. He said that every producer leaving a co-op puts greater financial pressure on those who remain.

The open market price for Rhone wine has risen from €100 per hectolitre a few years ago to €135 today, Roux said.

‘When the market is rising, negociants fight hard for the grapes, but they will have no loyalty when the market drops again,’ Roux said.

Frederic Lavau, managing director of Maison Lavau, a negociant winemaker in the Vaucluse, confirmed to local newspapers that he had sent 5,000 letters to winemakers. ‘We are simply contacting winemakers offering an alternative,’ he said. ‘It’s a free market.’

Roux said, ‘Certainly it is a free market, but this is upsetting the usual balance. The real issue as we see it is a war between the negociants. We are the collateral damage.’