The Policy attaches "great importance" to Green Belts, the fundamental aim of which is to prevent urban sprawl by keeping land open.
Planning permission should not be granted on Green Belt land unless "very special circumstances" exist, the NPPF said. The potential harm to the Green Belt must be clearly outweighed by other considerations.
The House of Commons' note highlights that there are objectors to the strict protection given to Green Belts in planning policy. The note acknowledges comments by international economic advice body the Organisation for Economic Co-operation and Development (OECD), which argues that there is scope to make more land available for building houses.
"In particular, Green Belts constitute a major obstacle to development around cities, where housing is often needed. Replacing Green belts by land-use restrictions that better reflect environmental designations would free up land for housing, while preserving the environment," the OECD said.
Green Belts serve five purposes, the NPPF said. They must check the unrestricted sprawl, prevent neighbouring towns merging, safeguard the countryside from encroachment, preserve settings and historic towns and assist in urban regeneration.
The Green Belt has not been reduced in size, the House of Commons' note said, which is in contrast to what most people believe. In 1997 the total size of Green Belt was 721,500 hectares, which had increased to 1.6 million hectares at 31 March 2011.
Research by Natural England concluded that whilst Green Belts are "fulfilling their purposes" in safeguarding the countryside from encroachment, preserving the character of historic towns and assisting with urban regeneration, they are failing in other areas.
Development is a third lower in Green Belt than urban fringes, they have assisted in directing the vast majority of residential developments to brownfield sites and have helped to designate world heritage sites, Natural England said.
It is argued that there should be a review of Green Belt boundaries, to update them to take account of today's needs, the Campaign to Protect Rural England said.
"[Green Belt] was designed for a different time, and it is now working against the ideal of sustainable communities which hope to encourage people to work, rest and play in the same local area," it said. "We recommend continuing support for this policy of selective review of green belt in the South East Plan."
