The NFU has lashed out at Morrisons, accusing it of having a "provincial" attitude to its dairy farmers.
The retailer had done nothing to engage with the industry in the three years since it bought Safeway and the NFU had run out of patience, said chief dairy adviser Tom Hind.
"We always hoped Morrisons would make the transition to being a national retailer," he said. "However, it hasn't lost the mindset of a small, provincial retailer from Yorkshire."
Efforts to engage with Morrisons bosses over the crisis in dairy farming had met no success, Hind added. "They're not even returning our calls any more."
He called on the retailer to follow the lead of multiples like Tesco, Sainsbury's and Waitrose, who had made commitments to pay a fair milk price and work closely with their suppliers.
Morrisons had to make more effort to add value to milk by differentiating its offer, he added.
The NFU's outburst contrasts with its praise for Tesco's high-profile rise in milk prices, which is being rolled out next month.
One hundred and thirty-eight of Tesco's Scottish dairy farmers will be among the first to benefit.
They have already signed the new contracts and will start to receive 22p/litre for the milk they supply after 1 July compared with prices as low as 17ppl. They sell their milk to Robert Wiseman Dairies, the Glasgow-based processor that provides 60% of Tesco's milk requirement.
Tesco's other supplier Arla is also preparing to roll out the contracts in July. By the end of the year all 850 farmers supplying milk to the retailer will be on the enhanced contracts, and their milk will be collected, processed and packed on separate lines.
"The speed Tesco has put their scheme in place is in total contrast to the inertia at Morrisons," Hind said. Morrisons said it had met the NFU this week and would listen to its concerns.