An official from Ivory Coast - the world's biggest cocoa producer - said they would "fight until the end" against the directive.

The Ivory Coast's Minister for Exports, Guy-Alain Gauze, told the BBC his country planned to lobby both European governments and consumer associations to try to convince them not to allow any cut in the cocoa content of their chocolate bars.

British chocolate contains vegetable fat

Ghana, whose economy is largely based on cocoa production, also denounced the EU proposal.

A Finance Ministry official described the move as "a stab in the back of cocoa producers and a wake-up call to producers to think of their future".

He said he would urge that "cocoa producers come together and plan strategies", including slapping taxes on imports from EU countries.

Traders say the new rules could cut cocoa consumption in Europe by up to 1,000 tonnes a year.

Livelihoods at stake

Cocoa grows in a belt around the Equator - and is a mainstay of many West African economies with millions of people depending on it for their livelihood.

European chocolate is high in cocoa content

Cocoa-growers have already suffered recently with prices for the bean falling sharply over the past year. They hit a six-year low in April.

The text approved by EU countries and the EU Commission, once adopted, would allow manufacturers to sell chocolate with added vegetable fats.

The fats would replace cocoa butter up to a limit of 5% of total weight and could still be sold as chocolate throughout the EU.

If the decision is approved by the European Parliament, then it is estimated that financial losses among developed countries could exceed $500m

However some West African countries, including Burkina Faso and Mali, stand to benefit.

Both countries export shea butter - from the nut of the Shea tree - which as a substitute for cocoa butter could make inroads into the lucrative chocolate market.

Beneficiaries

However, the British and Irish chocolate industries are expected to be the main beneficiaries of the proposal, opening up a vast new market for their products, after the end of a 25-year wrangle over exports to the EU.

UK-style milk chocolate, with a high fat and low cocoa content, has always been considered inferior on the continent, and several EU countries have in effect blocked imports on the grounds that the UK product is not "real" chocolate.

EU countries such as Belgium only recognise chocolate made purely with cocoa butter as the real thing.