Farmers have condemned moves to force them to leave fields uncultivated, warning that as much land as possible should be used to grow more crops and create jobs.
They also argued that plans to pay them to leave land fallow for wildlife could backfire and damage efforts to protect the environment.
Proposals have been floated by the Government to reintroduce a "set-aside" scheme similar to one abandoned two years ago.
Hilary Benn, the Environment Secretary, told the National Farmers' Union conference yesterday that action needed to be taken to tackle the fall in numbers of farmland birds.
But Peter Kendall, the NFU president, said the priority should be to boost food production. He said agriculture is one industry with reasonable prospects this year and should be at the heart of the economy.
Mr Kendall told the conference: "We are in a new era where we must produce more and at the same time impact on the environment less."
He warned that if his members were forced, under the rules for getting their subsidies, to introduce set-aside measures, many would be put off environment schemes which benefited the countryside through a range of measures such as planting hedges.
"Our proposed voluntary action plan is ambitious and we are determined it will achieve far more than any blunt regulatory stick," he said.
But the RSPB welcomed the government scheme, saying about 5 per cent of land would be needed for key projects, such as providing unsown plots in fields to help skylarks nest.