Farmers had lobbied for an increase in the permitted size to 600 square metres but the consultation document published today suggests 500 metres as the recommended option.
The consultation also recommends that the installation of anaerobic digestion plants, which use organic waste to produce biogas which can be used as a fuel, up to 500 square metres be classed permitted development.
Commenting on the consultation, environment minister Alex Attwood said: "The agriculture industry represents a vital part of the economy. These proposals, which are the most generous in these islands, will eliminate unnecessary red tape to enable agriculture to grow in a challenging economic climate. I want to help expand our agri-food business by 40 per cent in the next few years. That is what producers tell me they hope to achieve – these changes can help the industry to do so."
"Increasing the range of agricultural development that no longer needs planning permission will make it easier for farmers to undertake development. But these changes strike an essential balance. They free up farmers to make improvements with safeguards to protect neighbours and ensure that development is of an appropriate scale and character."
Atwood said it is anticipated that the proposals will become law in Spring 2013.
The consultation runs until 18 January 2013 and can be read here.