Hundreds of dairy farmers have blockaded three processing plants in a protest at the price they are paid for their milk.
Supporters of Farmers For Action used tractors to block a Robert Wiseman Dairy plant near Bridgwater in Somerset.
Dairy farmers are angry about cuts of up to 2p a litre in the amount they receive from major milk processors. Many fear the shortfall will force them out of business.
The action is the latest in a series of protests by farmers who are angry that they could be paid less for their milk than the cost of producing it.
David Handley, chairman of FFA, warned that more blockades could take place.
Speaking from the blockade near Bridgwater, Mr Handley said that, if the financial situation for farmers continued, they could be forced to make the "ultimate sacrifice" and cut off the milk supply at source, keeping it on the farms.
"These people have got greedy, and they have squeezed us and squeezed us to the point we have got to. We have got to fight for the industry because if we don't the industry is going to go," Mr Handley said.
He said there were around 550 farmers and 120 tractors between the Bridgwater plant and a nearby Morrisons supermarket distribution centre.
James Small, 36, a livestock farmer on the Mendip Hills in Somerset , said he supported his dairy colleagues at the protest near Bridgwater.
"There are an awful lot of young people, who obviously want to have a future in dairy and farming in general, and they're voicing their concerns about whether there will be a future given the current crisis. The sense of frustration and anger is palpable among the people here - they all feel a huge injustice about it all," he said.
Robert Wiseman Dairies said: "We fully understand the strength of feeling among dairy producers and continue to engage with those with an interest in the dairy supply chain.
"It is important to stress we are not in a position to fund a milk price at the level it was prior to the global collapse in the value of cream. It is our hope that the market for liquid milk and bulk cream which is at the core of this issue will quickly find a balance which will allow us to return improved prices to farmers."
Celebrity chefs Jamie Oliver and Hugh Fearnley-Whittingstall have stepped into the debate and urged the public to boycott some supermarkets.