Farmers across East Anglia are likely to refuse to grow extra sugar beet for a new bioethanol fuel plant.
The NFU claims farmers are enthusiastic about such uses for their crop but a price of £10 a tonne was well below production costs.
British Sugar insist the price is the best for many years for the "C" grade beet they are targeting.
Cole Carter from British Sugar said this grade was grown as a quota backup in case crops were hit by bad weather.
Row to 'continue'
Ross Haddow, of the NFU's sugar committee, said no farmer was going to grow extra beet for bioethanol fuel production at such a price.
The row was likely to continue because "farmers will plan to be extra careful and produce just enough to meet their quota commitments in future", he added.
And the price of £10 a tonne would persuade many to seek out other more profitable markets, said Mr Haddow.
The "C" grade sugar beet was previously offered for sale on the world market.
But new world trade rules agreed this year has closed this outlet to European producers who had been accused of "dumping" and damaging more efficient producers.
Mr Carter from British Sugar said they would use any excess sugar beet in their 70m litre a year plant being built at Wissington near Downham Market in Norfolk.