UK military defence spending is the third largest area of public government expenditure. For 2007/08 the total expenditure was £1.8 billion for the principal activity with a GVA of £468 million, and £1 billion for ancillary activities. A large amount of public expenditure has recently been directed towards building of new warships with £1150 million spent on shipbuilding and repair in 2006/07. Activities and hence the location of the value to the economy are mainly related to the location of the naval bases and exercise areas. The Navy employs 38 600 people and 5200 civilians and local economies also benefit from activities associated with the naval bases.

Military defence activities in the marine environment largely involve training, surveillance and monitoring, and transport. Designated exercise areas can be very large, and given the need for a certain amount of security there are uncertainties on the exact location and frequency of training activities within these areas. This hampers a spatial and temporal assessment of environmental pressures within the sector. Key pressures are likely to include noise from sonar and underwater explosions, habitat damage and introduction of marine litter and contaminants.

A sustainable development strategy was published by the Ministry of Defence in 2008 and provides a number of objectives, measures and targets for changing the way that activities are carried out in order to reduce pressure on the marine environment, climate and communities.