The Socialist Party office in the southern city of Carcassonne was hit buy an explosive device in the early hours of Wednesday morning.

The explosion caused windows to be blown out and part of the ceiling to collapse. Windows at a school across the road were also blown in by the force of the blast.

No one has so far claimed responsibility for the attack but graffiti left at the scene suggests so called wine militants may have been behind it.

The letters CAV were sprayed on the wall outside the offices in blue and red paint. CAV stands for Comité d’action Viticole (winemakers action committee).

The surname of France’s agriculture minister Stephane le Foll was also sprayed on the wall.

According to the Independent newspaper in Montpellier the initial inquiry suggested a gas cannister was used in the blast. The newspaper also claimed a party meeting had taken place at the offices just a couple of hours before the explosion.

Wine producers have in recent years, let off their anger in the direction of the authorities after becoming unhappy at the influx of cheap foreign imports, low prices and unfair competition.

There is also a suggestion that wine growers are unhappy at the delay of a government bill which would have seen them receive 15 percent of sales in advance.

Offices belonging to the ministry of agriculture have been targeted with explosive devices in the past and former President Nicolas Sarkozy was sent a video message in which balaclava wearing militants threatened violence if the president did come to the aid of struggling wine growers in Languedoc-Rousillon.

Regional Socialist Party chief Eric Andrieu condemned the action saying ‘’nothing justifies such acts’’.

"I am sorry you can always discuss things. I think the people behind this have not realized the danger of their actions.

"to put a bomb like that in the city center during Festival de la Cité, at midnight when there are still people in the streets."

"It has been signed by the CAV but we are trying to identify any claims of responsibility that may explain the act," he added.

The country’s Agriculture Minister Le Foll also expressed his dismay at the militant action and defended the government’s efforts to protect the wine producers.

"When it comes to wine production, France has managed to obtain many things from the latest negotiations at European level.

"I do not understand this attitude and the use of such violence in this incident. »Wine militants suspected of bombing Socialist party offices