The cost of the UK’s strategic nuclear deterrent

Research Briefing, 12 August, 2025 Claire Mills, Esme Kirk-Wade, https://commonslibrary.parliament.uk/research-briefings/cbp-8166/

Since the acquisition of the UK’s first strategic nuclear deterrent in the 1950s, the cost of procuring and maintaining it, and which Government department should finance it, has always been a matter of debate.

Ascertaining precise costs for the nuclear deterrent can be difficult, as this information is not easily available from public sources. The nuclear deterrent is also supported by an overarching, and complex, network of programmes, infrastructure, equipment and people, which is referred to as the Defence Nuclear Enterprise (DNE). Separating out individual costs for the nuclear deterrent from within that structure is not straightforward, particularly since 2023 when the government started reporting all nuclear-related spending as a single line (the DNE) in its departmental estimates.

Synergies between the civilian nuclear sector and the defence nuclear enterprise complicate that picture further.

Cost of the existing ‘Trident’ nuclear deterrent

The UK’s nuclear deterrent is provided by four Vanguard-class ballistic missile submarines (SSBN) which house the Trident II D5A missile and associated Mk4A/Holbrook warhead. The decision to procure Trident, as the nuclear deterrent is often referred, was taken in the early 1980s. Spending on the programme was largely complete by the time of the 1998 Strategic Defence Review. Total acquisition expenditure on the programme was £12.52 billion, which equates to approximately £23 billion in 2024/25 prices.

Prior to 2023, annual in-service costs, which also included the costs of the Atomic Weapons Establishment (AWE) and the Nuclear Warhead Sustainment Capability Programme, basing, decommissioning and disposals, were estimated at 6% of the defence budget (£3 billion for 2022/23). In 2023, the decision was taken to bring all nuclear-related programmes and expenditure, including the in-service running costs of the deterrent, under one heading: the Defence Nuclear Enterprise (DNE), and to ringfence it within the MOD budget. The intention is to provide greater flexibility within the nuclear programme and to try and insulate the rest of the conventional equipment plan from any changes in nuclear spending. In doing so, direct comparisons of in-service costs for the nuclear deterrent over time are no longer possible.

Replacing the nuclear deterrent

A programme is currently underway to replace the Vanguard-class submarines from the early 2030s.

The estimated cost of the design and manufacture of a new Dreadnought- class of four SSBN is £31 billion, including inflation over the life of the programme. A £10 billion contingency has also been set aside, making an upper-end estimate of £41 billion in total acquisition costs for the Dreadnought class. In May 2025 the Ministry of Defence said that £3.37 billion of the contingency had been accessed as of March 2024. It also said that the remainder had been allocated to future years, suggesting that the full £10 billion in contingency funding will be spent.

In 2016 the goverment said that it expected in-service costs for the nuclear- deterrent, once the new Dreadnought SSBN entered service, to continue at approximately 6% of the defence budget. Following the decision in 2023 to amalgamate all nuclear-related spend under a single DNE budget, however, the government said that an “equivalent comparison” for future in-service costs was no longer possible.

A programme to replace the UK’s nuclear warhead was also confirmed in February 2020. In the 2025 Strategic Defence Review, the government announced £15 billion for the programme within the current Parliament (to 2029).

Wider costs

The decision to amalgamate nuclear spending under one budget heading: the Defence Nuclear Enterprise (DNE), reflects the increasing interdependence between the nuclear deterrent and the Royal Navy’s other conventionally armed nuclear-powered submarine programmes, including the new AUKUS-SSN being developed in conjunction with the US and Australia. This is particularly relevant to the costs associated with basing, infrastructure and nuclear propulsion.

There are various costs associated with replacing the nuclear deterrent that are not part of the capital costs of the Dreadnought programme or the sovereign warhead programme, but fall within wider spending on the defence nuclear enterprise. Those costs include the UK’s participation in the US-led Trident Service-Life Extension programme, extension of the service-life of the current Vanguard-class SSBN, and various basing and nuclear infrastructure projects.

Spending on nuclear programmes across of the whole Defence Equipment Plan to 2033 is currently forecast at £128 billion. That represents a £10 billion increase on the original forecasts in the 2023-2033 equipment plan.

Who will pay for it?

In line with convention, the Dreadnought programme will be funded from the Ministry of Defence’s departmental budget.

There has been a longstanding debate over budgetary responsibility for the nuclear deterrent, with frequent calls made for the capital costs of the replacement programme to be removed from the MOD budget.