The UK has just under 10m cattle and calves plus around 32m sheep and lambs.
David Handley of Farmers for Action, who keeps 500 sheep and 100 cattle on his Monmouthshire farm, said: “The amounts of methane produced by farming are tiny compared with the emissions from transport and other sectors.
“But these rules and regulations are devastating the sector along with the UK’s ability to produce its own food.”
It comes after warnings from the CCC that the UK is off track to meet its 2030 climate targets.
In its latest letter to Mr Miliband, it said: “Setting a target is not enough. The UK must back up its international commitments through actions here at home.”
Claire Coutinho, the shadow energy secretary, said such massive cuts risked generating public unrest. “If we increase the cost of energy, make people change their diets, or generally make life hard for people in this country whilst they see carbon emissions rocketing in places like China, it will lead to public unrest.”
Tania Kumar, a director at the Confederation of British Industry (CBI), added: “Today’s CCC advice highlights the important partnership between business and government to scale up investment. However, it’s clear that to deliver against our 2030 target and go even further for 2035 requires a step change in action.”