British-produced food may disappear from many supermarket shelves within months due to the "crisis" facing the farming industry, a union has warned.
Meurig Raymond, president of the National Farmers Union (NFU) of England and Wales, said many farmers faced "big decisions" about whether to leave the industry in the next few weeks as they struggle to pay bills and face rising debts.
Farming leaders have met for an emergency summit in central London today as falling milk prices push those in the industry to "sheer desperation".
Speaking outside the summit, Mr Raymond said: "Obviously the industry is in crisis. There's despair within our members.
"I've been farming for 45 years and this is the worst I've known, particularly the dairy sector and the lamb sector. We've seen a 30% fall in milk prices in the last 12 months and we've seen good quality new-season lamb being sold at least £15 per animal less than last year. It's a crisis I've haven't seen in my farming career."
Mr Raymond said many farmers faced "big decisions" in the next few months. "For lots of farmers there's a cash flow issue," he said. "They're finding it difficult to pay bills, the overdrafts are increasing. Unless things improve, they may well have to make some big decisions in the next couple of months."
Protesters have been taking part in the Milk Trolley Challenges, blockading distribution centres and even bringing cattle into supermarkets to raise awareness of their plight.
The challenge sees farmers removing all cartons of milk from shops including Asda, Morrisons and Lidl before paying for it and taking it away, or dumping it at the checkout.
Mr Raymond said he was "delighted" British consumers appeared to be on the side of the farmers. He added: "I just plead with consumers at this time to look for Britishness, look for the Red Tractor, then they're guaranteed top quality assured food.
"If the farmers exit the industry, then British food may not be on the supermarket shelves in months and years to come."
Milk prices have been falling steadily - with Arla announcing a price cut of 0.8p per litre, taking the standard litre price to 23.01p for its UK members.
Farmers estimate that it costs between 30 and 32p to produce each litre of milk - meaning some are losing almost 10p per litre
A survey of milk drinkers found they would be willing to pay £1.28 for four pints of milk. Supermarket prices currently range from 89p to £1.
David Handley, chairman of Farmers For Action (FFA), is attending the summit, which will also examine prices paid to arable and lamb farmers. He said: "We are not asking them to put prices up to shoppers, we are saying there is such a margin between the farmgate price and the price the retailers are charging customers.
"This isn't farmers crying wolf, they fear for their future and for the future of their children. There is sheer desperation. People are so, so desperate."
Farming unions have called for ministers to hold a joint meeting with them to find solutions to the problems. A spokeswoman for the Department for Environment, Food and Rural Affairs (Defra) said: "We maintain a regular dialogue with farming unions and industry. We look forward to discussing these issues with them further."
A British Retail Consortium spokesman said: "There is no connection between the price of milk in supermarkets and the price retailers pay farmers for their milk.
"The retail industry pays a fair price with individual retailers using different payment models. We understand the current frustration of farmers but it is wrong to blame retailers."