Dairy Farmers of Britain last week announced it was dropping its standard milk price by 2.2ppl to 20.16ppl from April 1, its third reduction since November.
First Milk also cut its standard price by 1.25ppl to 22.58ppl from April, while Arla is dropping 1ppl to 23.79ppl from May. First Milk and Dairy Crest are also making reductions to their cheese prices.
NFU Dairy Board chairman Gwyn Jones accused processors of "trampling the green shoots of recovery in the industry underfoot". Jones had previously claimed that Tesco's decision only to drop its milk price by just over 1ppl meant processors would have no justification for further drops.
Jones added weak contracts allowed buyers to recoup costs at the farmer's expense and reiterated his calls for more robust terms.
DFB claimed a significantly weaker dairy market and heavy competition in milk and cheese had put huge pressure on margins.
"In setting the April milk price the board has had to take into account our short-term fall in revenue, the need to quickly conclude the reshaping of the business, and the requirements of our banking covenants," said DFB chairman John Grantchester.
The Farmers' Union of Wales said news of the price cuts would "shatter" producer confidence at a time of low milk supply. "Farmers are at the end of their tether and it is vitally important that processors and supermarkets stand by the industry," said milk and dairy committee chairman Eifion Huws.