This was the key message from the Liberal Democrat shadow secretary for Defra, Tim Farron to the National Farmers Union Conference in Birmingham this week.

Mr Farron said that at a time when the indicators point towards growth and opportunity, much of British farming - particularly in the livestock and dairy sector - is struggling.

"We have price instability, a lack of investment in research and development and a steady exodus of farmers from the industry," he said.

He said that farmers are leaving the industry because they cannot get a decent and reliable price for their produce.

"I am not here to demonise supermarkets, but I am here to make it absolutely clear that the Liberal Democrats believe that the biggest single problem facing farming today - whether it be in Cornwall or the Congo - is unfair trade.

"The power of the buyers, mostly the retailers, to offer a take-it-or-leave-it subsistence price to the relatively powerless producers."

He added: "We demand an end to this - we demand fair trade for British farmers too."

He said the situation is counterproductive, because the retailers are threatening their source of supply by offering such low prices.

"It is the greed of the supermarkets that is contributing to the exodus of many farming families from the industry.

"That's why our dependency on imports is rising," Mr Farron said.

He pointed out that compared to 1997 the UK imports 20 per cent more vegetables, 30 per cent more meat and three times the number of eggs.

He said the supermarkets are taking advantage of the system that has been allowed to grow and he called for fair regulation of the food market to encourage increases in production in British agriculture.

Mr Farron, welcomed the recent appointment of a supermarket ombudsman, but called for a stronger force to support producers.

"We want a proactive food market regulator, who would constantly monitor prices and enforce the code of practice," he said.

He added that he did not want the regulator to set prices but prevent farm gate prices being fixed.

"The supermarkets have the ability to pay a fairer and more stable price and to continue to retail at affordable prices," he said.

"There is fat in the system. It is on the retail side. You know it and they know it."