The Conservative Party is in favour of Britain retaining a nuclear weapons system, and so is the Labour Party. To that end, both are committed to the replacement of the four submarines built in Britain from which US-supplied Trident II missiles carrying nuclear warheads can be launched.
Labour in government initiated the process of replacement by publishing a White Paper, The Future of the United Kingdom's Nuclear Deterrent, in December 2006. This recommended that the new system should provide 'continuous at-sea deterrence' (CASD) as the current one does - in other words, that at least one submarine be on patrol armed with Trident missiles at any time. The White Paper left open the possibility that this capability could be provided by three submarines instead of the existing four. The White Paper proposals were approved by the House of Commons in March 2007.
The final decision on the issue is due next year. Irrespective of the outcome of the general election, there will be an overwhelming majority in the House of Commons in favour of building the submarines necessary to maintain 'continuous at-sea deterrence', though the SNP, Plaid Cymru, and a number of Labour backbenchers will vote against. The replacement of the present Trident submarines is certain to proceed.
On 9 April 2015, Minister of Defence, Michael Fallon, was tried to suggest that it won't proceed if Labour has to rely on the SNP for a majority after the general election. This piece of fantasy was invented by the Conservative election machine for the purpose of mounting a personal attack on Labour leader Ed Miliband, attacking him personally being the main thrust of the Conservative electoral campaign at the moment.
There is no doubt that the UK will have a submarine-based nuclear weapons system that could remain operational into the 2060s. It will cost the British taxpayer about £25 billion to build the replacement submarines and the related infrastructure, plus about £2 billion a year to operate them, that is, upwards of £100 billion during the lifetime of the system.
Deterrent independent?
Conservative and Labour advocates for the system describe it as an "independent" nuclear deterrent. On 9 April, Michael Fallon said that, if a Labour government scrapped it, this "would shatter the 60 year consensus that has existed among governments of all colours in favour of an operationally independent nuclear deterrent". Labour responded by insisting that "Labour is committed to maintaining a minimum, credible, independent nuclear deterrent, delivered through a 'continuous at-sea deterrent'". But is Britain's nuclear deterrent really "independent"?
At least eight (and perhaps nine) states ¬in the world now possess functional nuclear weapons and the means of delivering them. All of them, bar one, manufacture and maintain their own nuclear weapons and the means of delivering them. All of them, bar one, have complete control over the use of their systems. In other words, all of them, bar one, possess what can reasonably be described as an "independent" nuclear deterrent that doesn't rely on another state to provide vital parts of it.
The exception is Britain. China has an "independent" nuclear deterrent. So has France, India, Israel, Pakistan, Russia and the US - and perhaps North Korea. Britain hasn't.
Unlike other states that have nuclear weapons systems, Britain is dependent on another state to manufacture an essential element of its only nuclear weapons system - the Trident missiles that are supposed to carry Britain's weapons to target. These are manufactured by Lockheed Martin in the US.
And Britain's dependence on the US doesn't end with the purchase of the missiles - Britain depends on the US Navy to service the missiles as well. A common pool of missiles is maintained at the US Strategic Weapons facility at King's Bay, Georgia, USA, from which the US itself and Britain draw serviced missiles as required.
There is some doubt about the degree of "operational" independence that Britain enjoys in respect of its nuclear weapons system (of which more later). But there is no doubt that Britain is dependent on the US for the manufacture and maintenance of a key element of the system. So, to call it an "independent" nuclear deterrent is fraudulent.
Independent foreign policy?
The plain truth is that, if Britain doesn't maintain friendly relations with the US, then it won't have a functional nuclear weapons system, despite having spent billions of pounds of British taxpayers' money on it - because the US would simply cease providing Britain with serviceable Trident missiles.
So, there is a strong incentive for Britain to follow the US in foreign policy, since independence from the US in foreign policy could lead to its nuclear weapons system becoming non-functional. Sustained opposition to the US in foreign policy certainly would. As long as Britain is tied to the US by a requirement for US-supplied and maintained missiles for its nuclear weapons system, it cannot have a wholly independent foreign policy.
In these circumstances, it is highly unlikely that Britain would use its nuclear weapons system to strike a target without the approval of the US, whether or not it is theoretically possible for Britain to do so. So, it is absurd to describe it as "independent" nuclear deterrent.
The above applies to the UK's current nuclear weapons system. But it applies equally to the proposed replacement. To ask the British taxpayer to fork out upwards of £100 billion in the pretence that the UK will continue to possess an "independent" nuclear deterrent is fraudulent.
Surprisingly, December 2006 White Paper conceded that our US-dependent nuclear deterrent will become non-functional if relations sour with the US. Paragraph 4-7 puts it this way:
"We continue to believe that the costs of developing a nuclear deterrent relying solely on UK sources outweigh the benefits. We do not see a good case for making what would be a substantial additional investment in our nuclear deterrent purely to insure against a, highly unlikely, deep and enduring breakdown in relations with the US. We therefore believe that it makes sense to continue to procure elements of the system from the US."
It would be more honest to say that Britain is incapable of building a credible deterrent relying solely on UK sources. It lost that capacity over 50 years ago with the termination of the Blue Streak ballistic missile project, which is why we ended up buying first Polaris, and then Trident, submarine-launched missiles from the US.
Operationally independent?
British Governments have always insisted that Britain's nuclear weapons system is "operationally" independent of the US. The December 2006 White Paper (4-6) states that "the UK's current nuclear deterrent is fully operationally independent of the US". Apparently, if a British Prime Minister decides to press the nuclear button, it is impossible for the US to stop the launch of missiles or prevent them delivering British nuclear warheads to the selected target. Maybe so.
Is a British Prime Minister really free to strike any target he/she chooses in this world with nuclear weapons, at a time of his choosing, using US-supplied missiles? I doubt that the US would sell any foreign power - even a close ally - a weapons system with which the foreign power is free to do catastrophic damage to US allies, not to mention the US itself. Surely, the US must have a mechanism, under its explicit control, to prevent the targeting of states that it doesn't want targeted?