Dairy farmers from across the UK have been "pushed to the brink" by cuts to the price of milk, a farmers' union representative has told a summit.
About 2,000 farmers gathered in London to protest at the latest cuts by processors of up to 2p a litre.
The NFU's Meurig Raymond said: "Society has to recognise what these dairy farmers have been put through by a market place that doesn't work".
The government said it hoped to see a "fair deal".
Agriculture Minister Jim Paice said he was close to getting agreement on a revised voluntary code for dairy contracts from milk processors.