Farmers' leaders are worried that a meat price war will hit producer incomes.
Tesco recently ran a promotion offering 25% off prices of fresh meat products.
This week Asda hit back by slashing prices on fresh lamb, beef and pork.
MLC marketing director Richard Lowe said price-cutting "mortgaged future sales" because customers simply bought more and put the extra in the freezer for later.
He added: "There's a bit of machismo about this, a 'we can do what you can do' attitude.
"It puts pressure on supply chains because ultimately the margin discount has to be funded from somewhere.
"Either the retailer takes it out of their own margins or the processor has to fund some of the reduction, but you can't sustain it for long without livestock prices being affected."
Lowe added: "It's a depressing practice because meat is not struggling to such an extent that it needs this type of deep-cut promotional activity."