Biotechnology companies in the US are softening their self-imposed moratorium on planting certain types of crops in major food-producing regions.

Under the moratorium, growers were banned from planting certain types of GM corn in the Midwest farm belt and from planting some types of rape plant on the Canadian prairie, to prevent crop contamination.

The moratorium has, however, angered Iowa politicians who claim that the policy discriminates against their state, which is aiming to build up a lucrative industry around biotech crops such as those developed for pharmaceutical purposes.

The revised policy means that the Biotechnology Industry Organisation would leave the decision of where to plant GM pharmaceutical crops up to federal regulators, which have permitted experimental corn plots in Iowa. A spokeswoman for the biotech organisation said the group did not want to appear to be discriminating against certain parts of the country, reported The Wall Street Journal.