SCOTTISH farmers are to join a massive march on Westminster today to protest at milk prices they claim will end hundreds of years of traditional dairy production.

Around 40 dairy producers from north of the Border will join 2000 others from across the UK to call for greater regulation of milk pricing processes.

They warn if the system is not changed many will have to stop milk production or go out of the business altogether.

Farmers blame a complicated pricing structure in a marketplace dominated by the needs of supermarkets to have low prices at the tills.

Over-production of milk has meant the prospect of trader prices reaching as low as 25p a litre by August, while it costs farmers 30p a litre to produce.

The British Retail Consortium (BRC), for the supermarkets, insisted there was already sufficient legislation in place and added dairy processors, manufacturers and the big public sector buyers – such as schools and prisons – should also be held to pricing structures.

The National Farmers' Union Scotland said Westminster should take the lead in setting out a fairer pricing structure to save jobs and also to protect the future price of a pint of milk for consumers.

The union will join protesters, Farmers for Action, in a meeting with UK Farming Minister Jim Paice in London.

Gary Mitchell, NFU Scotland milk spokesman and a farmer from Stranraer, said a clearer system of contracts between supermarkets, milk traders and producers should be imposed.

He said: "We want a change in the legislation and a pricing code of practice introduced.

"There needs to be political pressure put on the retailers, and there needs to be more transparency in pricing."

Policies vary depending on whether a farmer sells direct to a supermarket or if they go through a milk trader – usually a farmers' co-operative. Some feel greater pricing powers for such co-ops would mean greater control over market conditions. Prices even vary between a litre of milk being sold to be used to make cheese and a litre being produced for resale.

David Shaw, an Ayrshire-based dairy farmer who also operates as a trader selling milk from 70 farms, said the existing practices were unsustainable.

He said: "If we can't stop this pricing policy my farmers are going to go out of business left, right and centre. All we want is a fairer slice of the cake."

Industry insiders estimate only around 30% of farmers in Scotland are on contracts that will still be viable if there is a change in prices, with one source saying part of the problem is that "a lot of the co-ops [who trade milk] are farmer-owned but not farmer-run".

Andrew Opie, BRC food director, said: "Supermarkets are the best payers in the milk market. Supermarkets only sell British milk but their customers don't need all the milk produced by UK dairy farmers.

"Only half of the milk British farmers produce ends up as liquid milk in bottles and cartons and only part of that is sold in supermarkets. The rest is sold by convenience stores, door-to-door or used in catering, schools and prisons.

"A number of supermarkets have dedicated milk supply chains which allow them to work closely with specific groups of farmers, guaranteeing how much the farmers get for their milk and helping them invest in the long-term sustainability of their businesses.

He added: "The pressure should be on other big buyers of milk – food manufacturers and the public sector – to show the same strong support for the industry that retailers do.

"The truth is, the dairy farmers in the best position are often those in supermarket supply chains."