The three main criteria state that -
- it must be in the National interest;
- there is no practicable alternative to development in a National Park;
- must be built in a way that minimises detrimental effects on the environment. 
The test was contained in Planning Policy Statement (PPS) 7: Sustainable Development in Rural Areas (formerly PPG7) PPS7 has now been replaced by the National Planning Policy Framework (2012), in which paras. 115/116 set out a differently-worded test.
- South Wales Gas Pipeline (2007)
- "Environmental conditions placed on South Wales pipeline". Department of Trade and Industry (National) (Press release). Government News Network. 7 February 2007. Archived from the original on 27 September 2007.
- until August 2004 the test was contained in its precursor - Planning Policy Guidance (PPG) 7: The Countryside – Environmental Quality and Economic and Social Development.
- Brotherton, D I (1989). "The evolution and implications of mineral planning policy in the national parks of England and Wales". Environment and Planning. A21 (9): 1229–1240. doi:10.1068/a211229.