Monsanto president and chief executive officer, Hugh Grant, wrote to DuPont board chairman Charles Holliday, stating that he views activities undertaken by DuPont as "misleading to the public and a serious break of business ethics far beyond honest competitor behavior."

Monsanto's claims relate to what it sees as a multi-year attack against the company surrounding Monsanto's acquisition of Delta and Pine Land, technology rights around Optimum GAT and DuPont's financial support of the Organisation of Competitive Markets - a group critical of Monsanto.

Grant's letter noted that DuPont declined to release non-financial contract terms of technology agreements so third parties could make their own determination as to the stacking rights.

"While DuPont is aware that it always had the right to stack a second mode of weed control like ALS with Monsanto's technology (such as has occurred with your first generation of STS technology now off patent) any current problem with stacking OGAT is a business decision of DuPont's making," Grant wrote.

"Your lobbying and communications that paint your company as a victim of limiting technology licenses is dishonest, disingenuous and downright deceitful."

The letter and a series of other documents related to the campaign have been posted on Monsanto’s website at www.monsanto.com/dupont-youbethej udge.