US farmers are growing the first corn plants genetically modified for the specific purpose of putting more ethanol in gas tanks rather than producing more food.

Aid organisations warn the new GM corn could worsen a global food crisis exposed by the famine in Somalia by diverting more corn into energy production.

The food industry also opposes the new GM product because, although not inedible, it is unsuitable for use in the manufacture of food products that commonly use corn. Farmers growing corn for human consumption are also concerned about cross-contamination. The corn, developed by a branch of the Swiss pesticide firm Syngenta, contains an added gene for an enzyme (amylase) that speeds the breakdown of starches into ethanol. Ethanol plants normally have to add the enzyme to corn when making ethanol.

The Enogen-branded corn is being grown for the first time commercially on about 5,000 acres on the edge of America's corn belt in Kansas, following its approval by the US Department of Agriculture last February. In its promotional material Syngenta says it will allow farmers to produce more ethanol from the corn while using less energy and water.

Meanwhile, campaigners say the corn will heap pressure on global food supplies and contribute to environmental degradation. They argue Enogen will lead to an increase in the amount of food crops going to fuel, leaving less for human consumption and leading to food price rises. That will lead to food price rises on the global market. "The temptation to look at food as another form of fuel to use for the energy crisis will exacerbate the food crisis," said Todd Post of Bread for the World, a Christian anti-hunger organisation.

Although individual events such as the Somalia famine are caused by a complex combination of factors, several studies have established that the expansion of biofuels has pushed up food prices worldwide, making it harder to afford for the poorest. A World Bank report released on Tueday says food prices that are now close to their 2008 peak have contributed to the famine in Somalia. Marie Brill, a senior policy analyst at ActionAid warned: "It's going to put even more pressure on a really tight market. It will be really tempting to farmers to take on this new more efficient ethanol form of corn."

The food industry is warning of the dangers of contaminating existing corn crops with the new GM corn. The same traits that make the modified corn so attractive to the ethanol industry – the swift breakdown of starches – would be a disaster for the food industry, turning corn chips into shapeless lumps, and stripping the thickening properties from corn starch.

Even a small amount of the amylase corn – one kernel out of 10,000 – could damage food products, according to data supplied to the North American Millers' Association by Syngenta. The organisation, like most food industry groups, has opposed the corn, noting failures to prevent cross-contamination from earlier GM breeds.

The European Union, South Korea, and South Africa have not approved its import.

Enogen also has to catch on among farmers. "I'm sceptical as a farmer," said Allen Jasper, who runs a cattle-feed operation near Whitten, Iowa. "The first thing I'm going to ask is how does it yield. Any time you try and change a corn plant and get it to do something that is not native to the plant you have to be sceptical of the yield."

Syngenta maintains the corn variety has a high yield, and that it has the appropriate safeguards to prevent cross- pollination. After Kansas, the company plans to expand its growing area to Nebraska, Iowa, South Dakota, and southwest Minnesota.

Farmers will grow the corn under contract to an ethanol production plant, getting a premium over regular corn. Buffer rows of corn will be planted. "This is a very slow ramp-up. This is not a broad acre crop at this point," said Paul Minehart, a Syngenta spokesman.

Steve McNinch, of Western Plains Energy, in Kansas, the only ethanol plant to have processed the new corn, said adding a small amount of amylase corn to the mix – about 10% – would increase production by 10%.