In United Kingdom town planning, the green belt is a policy for controlling urban growth. The idea is for a ring of countryside where urbanisation will be resisted for the foreseeable future, maintaining an area where agriculture, forestry and outdoor leisure can be expected to prevail. The fundamental aim of green belt policy is to prevent urban sprawl by keeping land permanently open, and consequently the most important attribute of green belts is their openness.
The Metropolitan Green Belt around London was first proposed by the Greater London Regional Planning Committee in 1935. The Town and Country Planning Act 1947 then allowed local authorities to include green belt proposals in their development plans. In 1955, Minister of Housing Duncan Sandys encouraged local authorities around the country to consider protecting land around their towns and cities by the formal designation of clearly defined green belts.
Green belt policy has been criticised for reducing the amount of land available for building and therefore pushing up house prices, as 70% of the cost of building new houses is the purchase of the land (up from 25% in the late 1950s).
The Government formerly set out its policies and principles towards green belts in England and Wales in Planning Policy Guidance Note 2: Green Belts, but this planning guidance was superseded by the National Planning Policy Framework (NPPF) in March 2012. Planning Authorities are strongly urged to follow the NPPF's detailed advice when considering whether to permit additional development in the green belt. In the green belt there is a general presumption against inappropriate development, unless very special circumstances can be demonstrated to show that the benefits of the development will outweigh the harm caused to the green belt. The NPPF sets out what would constitute appropriate development in the green belt.
According to the NPPF, there are five stated purposes of including land within the green belt: