On 1 April 2012, under the Localism Act 2011, the Planning Inspectorate became the government agency responsible for operating the planning process for Nationally Significant Infrastructure Projects (NSIPs).

NSIPs are major infrastructure projects such as new harbours, roads, power generating stations (including offshore wind farms) and electricity transmission lines, which require a type of consent known as ‘development consent’ under procedures governed by the Planning Act 2008 (PA2008). Development consent, where  granted, is made in the form of a Development Consent Order (DCO).

The PA2008 sets out thresholds above which certain types of major infrastructure projects are considered to be nationally significant and require development consent.

In England, the Planning Inspectorate examines applications for development consent from the energy; transport; waste; waste water; water; and business and commercial sectors. In Wales, it examines applications for energy and harbour development, subject to detailed provisions in the PA2008. Other matters are for Welsh Ministers.

Anybody wishing to construct an NSIP must first apply for consent to do so. For such a project, the Planning Inspectorate examines the application and will make a recommendation to the relevant Secretary of State, who will make the decision on whether to grant or to refuse development consent.

The relevant Secretary of State is the minister with responsibility for the area of government business that an application relates to. For example, the Secretary of State for Transport takes the decisions on applications for highway NSIPs.