Groups of dairy farmers have been emptying milk from supermarket shelves across the country in protest at the price paid for milk.
The protest, dubbed the Milk Trolley Challenge, sees protesters removing all cartons of milk from shops including Morrisons and Lidl and either paying for it and taking it away or dumping it at the checkout.
Arla, Britain's biggest milk co-operative, has announced a price cut of 0.8 p per litre - taking the standard litre price to 23.01p for its UK members.
Farmers say it costs between 30 and 32p to produce each litre of milk, according to British dairy organisation AHDB Dairy.
Last Thursday, a group of farmers emptied milk from supermarket shelves including Morrisons and Lidl in Yate, south Gloucestershire.
In a video of the protest, a woman says: "We're doing the Milk Trolley Challenge.
"This is due to the unfair milk price. We are clearing the shelves. Morrisons, you have been milked."
One protester shouts "too cheap, take it away" as the group loads cartons of milk into a line of trolleys in the store.
Further protests took place over the weekend, with shelves emptied at two Morrisons shops in Bude, Cornwall.
There have also been reports of farmers doing the Milk Trolley Challenge in Northern Ireland, where prices have dipped to an average of 19p per litre.
Meurig Raymond, president of the NFU, said: "The market situation in dairy, lamb and many other products is driving farming families to a desperate state with returns from the market failing to cover costs of production.
"Farmers have worked very hard to gain the respect and support of the public for great British food - now farmers simply want and need a fair return for years' of investment.
"Given the current situation some farmers have been driven to take direct action; the NFU supports protests that have a proper target and a clear objective.
"However, we believe that the best way for farmers to get a fairer return would be for consumers to demand British food.
"Our survey work has shown that 85% of people want to see retailers selling more British food. Now is not the time to alienate our loyal customers."
Figures published by AHDB Dairy show the average UK farmgate price was 24.06p per litre in May, a decrease of 25.4% of the amount paid to farmers in May last year.
A spokeswoman said: "Anecdotally, farmers are putting the costs of production at around 30/32 pence per litre, which demonstrates that for some, the price they receive will not cover what it costs them to produce the milk."
Farmers in Northern Ireland received an average of 21p per litre in May, a drop of 32.1% compared with the same month last year.
Protesters have been using Facebook to arrange Milk Trolley Challenges in Clitheroe in Lancashire and Cheshire.
Darren Blackhurst, Morrisons Group Commercial Director, said reduced global demand had created an oversupply of British milk, creating "difficult conditions" for many dairy farmers.
"At a constructive meeting on Wednesday with the NFU Dairy Board Chairman, we confirmed that Morrisons is not accepting any further cost price decreases from our suppliers driven by the falling farm gate milk price," he added.
A spokeswoman for Lidl said the supermarket worked closely with farm assurance schemes such as Red Tractor and RSPCA Freedom Food to champion British farming.
"Naturally, we are concerned about the challenges faced by British farmers currently as a result of volatility in global market conditions," she added.
"As such, we have pricing mechanisms in place which are monitored at regular intervals during the contract period to reflect market fluctuations and to ensure that our farmers continue to be paid a fair and accurate market price.
"Our cost prices are in no way linked to our retail prices and any reductions in retail prices are absorbed by Lidl."