After direct action protests against falling milk prices resumed in Shropshire on Sunday night, farmers stepped up their campaign on Wednesday, carrying out a blockade at the Morrisons depot at Bridgewater, Somerset.

Protest organisers said over 500 people, and up to 70 tractors, attended the Bridgewater demonstration, with similar numbers estimated to have attended the blockade of Muller-Wiseman's plant in Market Drayton earlier in the week.

Protest group Farmers for Action has held Crisis Meetings in Market Drayton, Frome and Carmarthen, where the group's policy of blockading distribution hubs and processing plants to draw attention to farmers' plight received overwhelming support. The next crisis meeting will be held next week in Penrith, Cumbria.

Falling values on the global market have depressed milk prices around the world; processors maintain this "unprecedented" market situation is behind price cuts – which in some cases have been made for six consecutive months. However, frustrated farmers maintain that cuts are unjustified and have taken returns for milk below the cost of production.

Even so, the NFU has refused to back the return to direct action this time around. In a statement on Wednesday, NFU president Meurig Raymond spoke of the union's involvement in the SOS Dairy campaign in 2012, when a spate of demonstrations and blockades led to the establishment of a voluntary code to govern relationships in the dairy sector.

However, Raymond continued, "Two years on… The NFU continues to hold regular meetings with all the main retailers and processors to hold them to account, ensuring any price rises go back to farmers and any prices falls aren't used as an excuse for unfair behaviour… Fighting for functioning markets and fairer contracts is ultimately the best way to achieve farm gate milk prices that fairly reflect the value of milk."

The union has said dairy farmers are facing a farmgate price drop of between 20-30 per cent in the past few months, and that retailers and processors have a duty to ensure their suppliers receive a fair price for their milk.

Commenting after this week's blockades, Farmers for Action Chair David Handley said, "The first peaceful protest went extremely well and I think all who took part deserve a pat on the back for the way they behaved and presented themselves to the multitude of media present covering the issues.  This campaign is all about telling consumers, the government and all who play a part in our milk supply chain, things are not right."

Speaking after the protest in Shropshire, Handley said, "I emphasise, despite the area, this is not Muller Wiseman.  All processors and retailers who currently extract money are targets within our campaign to get the message across.  UK dairy although not exempt from global issues, should not be sustaining the milk price cuts it currently is."

The FFA chair praised those who attended on Wednesday night, saying protestors had done "A grand job." He promised, "Further protests are planned for the coming week."

A Morrisons spokesperson said the supermarket is "really concerned about the impact" of ongoing price cuts. In a letter to the NFU, the retailer said, "New mechanisms to help the industry cope with this level of price movement must be developed. We at Morrisons are committed to doing this and are well advanced, as evidenced by our cheese contract which the NFU welcomed last year.

"We are re-tendering for liquid milk supplies because we are coming to the end of our current five-year contract in 2015, not in response to the current market situation. We fully recognise the increasing level of concern about falling prices as articulated by the NFU, and that is why I can assure… that a mechanism to address fluctuations in the market will be a feature of any new liquid milk contract."

Morrisons maintains that "Any promotions on liquid milk have been paid for entirely by us and not passed on to the processor or farmer."