What’s behind the deepening US-UK nuclear weapon cooperation?

The Mutual Defense Agreement (MDA) lies at the heart of the special nuclear relationship between the United States and United Kingdom. The nuclear relationship set up by the MDA is seen to be beneficial to both the US and UK by cementing the bilateral relationship in sharing of nuclear weapons technology, as well as enshrining a certain uneven power structure in law.

The White House has just announced that it has lodged the treaty’s once-in-a-decade renewal and amendment on the floor of Congress for formal ratification, and a similar though more secretive process is about to be initiated in London. The MDA is also highly symbolic of the core discrimination within the non-proliferation regime, whereby two states are not only given temporary recognition of the nuclear weapon status, but also give themselves license to transfer between themselves nuclear weapons technology and equipment relevant to carrying and delivering them, when this appears to be proscribed under the Nuclear Non-Proliferation Treaty (NPT). The MDA ought to be scrutinized by the UK Parliament just as it is by Congress in order to ensure accountability and transparency. These occasional renewals present an opportunity to reassess long term strategic choices that influence who we are and how we engage with the world and therefore deserve greater attention. For the government to formally lodge the MDA with Parliament just when all members have departed for their holidays and expect it to receive automatic ratification appears cynical and runs counter to the principals of open government.

What is the MDA?

The treaty essentially fulfils the conditions necessary for the UK to have a nuclear deterrent and binds the UK’s nuclear weapons policy to the United States, with implications for a variety of policies from diplomatic positioning to the choice of weapon systems. As the UK’s Atomic Weapons Establishment (AWE) stated in an annual report, once the MDA was signed in 1958 it ‘ushered in a series of technical exchanges which have been a cornerstone of life for our nuclear weapons community ever since’. Significantly, the designs of the current UK Trident warhead and the US W76 warhead are thought to be very similar, and there are references to the W76 being ‘anglicised’ at Aldermaston. The MDA, along with the updated 1963 Polaris Sales Agreement, also facilitates the leasing of Trident II D5 missiles from a common pool created, maintained and tested by the United States. Furthermore, under the auspices of the MDA, the UK and US are working to design a common missile compartment for their Vanguard and Ohio Replacement Programmes respectively. In 2002 the first joint UK/US sub-critical nuclear test, codenamed ‘Vito’ was conducted at a Nevada test site. Beyond this, the MDA governs more general collaboration between Aldermaston and the US nuclear labs that involves transfers of designs, technology and components and special materials, and the exchange of scientists and technicians. This can be useful not only to expand the ‘gene’ pool and to allow best practice to percolate between the institutions, but also could on occasion have been used to side-step controls that Parliament or Congress may from time-to-time attempt to impose upon their own labs.

Why is the MDA controversial?

The MDA is in a tricky legal territory, because it possibly contravenes US and UK obligations under the Non-Proliferation Treaty (NPT) signed in 1968 (ten years after the MDA was born). Article I of the NPT states that, ‘each nuclear-weapon State Party to the Treaty undertakes not to transfer to any recipient whatsoever [italics added] nuclear weapons or other nuclear explosive devices or control over such weapons or explosive devices directly, or indirectly’. In other circumstances, this article has generally been interpreted as prohibiting the transfer of nuclear weapons-related technology, including designs for warheads or the instruments to make them, or the essential materials and components. Yet, this is exactly what happens under the MDA.

Prior to the ratification of the previous amendment in 2004, BASIC, Acronym and Peacerights commissioned a legal opinion from Rabinder Sing QC and Professor Christine Chinkin that concluded that ‘it is strongly arguable that the renewal of the Mutual Defence Agreement is in breach of the Nuclear Non-Proliferation Treaty’. If the United States and UK renew the MDA and in fact increase their cooperation on the ‘development of safer, more secure, warheads’, they open themselves to charges of hypocrisy in regards to their current positions on the Iranian nuclear programme, and this is likely to be an additional grit in the wheels of the NPT Review process at a particularly sensitive moment. It was suggested by Peter Burt of the Nuclear Information Service that if Iran and North Korea signed a similar agreement, the UK and US ‘would be…screaming for the toughest of international sanctions’. It appears that the two countries are relying upon a combination of longevity of the arrangement, complacency on the part of those responsible to ensure accountability, and a certain degree of concealment, in the hope that this arrangement yet again slips under the radar. In fact, there is a degree of hiding the arrangement in plain sight on the basis that everyone knows the two countries collaborate in this arena, so what is the problem? The problem is that this strategy holds big risks for the NPT when many non-nuclear states are expressing a degree of disillusionment with it, and when there is clearly a strong expectation of failure in the review process at next year’s conference.

Why isn’t the MDA debated?

In 2004, the last time the MDA was renewed, parliamentary debate was blocked by statements from ministers saying that only ‘treaties with direct financial implications require the assent of Parliament because they affect revenue’. Furthermore, written questions to Ministers were mostly avoided by the government on the grounds of ‘national security,’ meaning that open discussion of the treaty would undermine national security. However, there is no written definition of ‘national security’ meaning that the Secretary of State is responsible for deciding the issue on a case by case basis.

The MDA was created and is upheld by a mutual commitment to nuclear weapons research, meaning that the UK is required to commit financial resources to weapons research if it is to receive assistance from the United States. As a result, the MDA has a direct financial implication for the UK government. Furthermore, the treaty contains serious military and political issues which affect the UK’s defence and diplomatic policy, meaning that Parliament should be encouraged to hold an open debate on the treaty. So far, the government has appealed to the Ponsonby Rule, which has been observed for well over a century and generally means that the treaty making prerogative of the Crown is used to sign treaties, after which they are tabled for 21 days (theoretically a period for debate), then ratified by the Crown and finally released to Parliament. Alongside blocking efforts by various ministries and individuals – for example, in 2004 Lord Bach stated that debating the treaty in Parliament “might well assist proliferation”.

A number of MPs have tabled Early Day Motion 153 calling for a debate “on any proposal to renew the MDA prior to ratification” because of the possibility that the UK is in violation of its NPT obligations. To date 19 MPs have signed the motion.


This blog post relied heavily upon the previous special report on the MDA by BASIC from 2004: Shining a torch on the dark recesses of the special relationship.

Share This

Copy Link to Clipboard

Copy