Celebrity chefs Jamie Oliver and Hugh Fearnley-Whittingstall have urged the public to boycott some supermarkets over cuts to the price of milk.
In a letter to the Times, Oliver and Fearnley-Whittingstall said it was "shocking" that many dairy farmers were to be paid less for their milk than it costs them to produce it, adding that the industry was becoming unviable.
Calling on consumers to boycott supermarkets who continued to use milk as a loss leader, they warned that thousands of family businesses would fail and the landscape would be threatened if the industry breaks down or becomes "super-industrialised".
They wrote: "It is shocking that many dairy farmers are to be paid less for their milk than it costs to produce it. Dairy farming in this country is fast becoming unviable.
"Milk is a brilliant food but we have all lost sight of its value. We pay more for bottled water than we do for milk - yet water bubbles out of the ground, while milk comes from livestock which need our care. How mad is that?
"Dairy farmers can't take industrial action. Their daily commitment to their herd makes it impossible. How cynical of retailers to take advantage of this.
"If the dairy industry expires, or becomes super-industrialised, it's not just thousands of family businesses that will go to the wall. Our whole landscape is threatened. All over Britain the patchwork of hedgerows and grass fields owes its existence to the traditional production of milk.
"It's time supermarkets stopped using milk as a loss leader. And if they won't take that initiative, then perhaps consumers will consider moving their custom from those who offer milk at crazy knockdown prices to those who will commit to giving dairy farmers a fairer deal. We're delighted to see the WI is already campaigning for just such action, and we urge everyone who drinks milk (that's pretty much all of us, of course) to do the same."
National Farmers Union dairy board chairman Mansel Raymond told MPs this week that farmers "will not have the heart to go into the winter" if milk prices stay where they are.
Dairy farmers are protesting against cuts of up to 2p a litre in the amount they receive from major milk processors and have warned that many are being pushed to the brink and may be forced out of business, pushing up the price of milk for consumers in the long term.
The latest cuts will see farmers paid around 25p a litre for milk, but Mr Raymond said the cost of production was 29p a litre, meaning a sale price of 29.5p was the minimum they needed to remain viable.
Dairy Crest - behind well-known brands Cathedral City, Clover and Country Life - is one of a number of milk producers that have slashed the price they pay farmers for milk after seeing the value of cream plummet this year.
It has admitted its milk price cuts "put pressure on our supplying farmers".
But the British Retail Consortium (BRC) said supermarkets were the "wrong target".
BRC spokesman Richard Dodd said: "They're actually the best payers for milk. Currently, 11 of the top 12 best-paying milk contracts are contracts paid by supermarkets.
"But supermarkets and their customers don't need all the milk produced by UK dairy farmers. Only half of the milk they produce ends up as liquid milk in bottles and cartons and only part of that is sold in supermarkets; the rest is sold by convenience stores, door-to-door or used in catering, schools and prisons.
"What we don't see is protesting farmers or TV chefs questioning the amount that the other big buyers of milk, who include manufacturers and the public sector, are paying and calling on them to show the same strong support for the industry that retailers do.
"A number of supermarkets have dedicated milk supply chains which allow them to work closely with specific groups of farmers, guaranteeing how much they get for their milk and helping them invest in the long-term sustainability of their businesses.
"That matters to retailers who want successful relationships that will provide the milk they and their customers need, not just now, but over the coming decades. But that can't be the answer for every farmer."