Jeremy Corbyn: … those countries have all been involved in conflicts, and we have come near to the use of nuclear weapons in the case of Korea and in the Cuban missile crisis in 1962. Clearly, their existence poses a threat. When the House debated Trident renewal in 2007, many Members took the view that Britain’s security depended on having nuclear weapons. If that was the case, someone could argue for any country in the world developing nuclear weapons on the basis that that would guarantee its security. As I have explained, the reality is that the vast majority of nations do not have nuclear weapons and do not want them. Although some are under a nuclear alliance such as NATO, many are not and do not possess nuclear weapons, yet have massive natural resources. Many countries in Africa, Latin America and Asia are part of nuclear weapons-free zones. That is my view.

Dr Julian Lewis: I appreciate that I will have the opportunity to speak after the hon. Gentleman, but I want to take him back to the point made by the hon. Member for Strangford (Jim Shannon). The hon. Member for Islington North (Jeremy Corbyn) said that if nuclear weapons were used, there would be dire effects on the environment and on the planet, but does he not recognise that people who believe in deterrents believe that the nuclear deterrent is constantly in use, because the use resides in the possession, which results in the deterrent effect on any other power against using such weapons against this country?

Jeremy Corbyn: The hon. Gentleman and I have debated that view, and I simply do not agree that they provide security. Yes, they are in existence every day and therefore clearly are potentially a threat to somebody, but it did not do the USA much good on 11 September 2001. Nuclear weapons were not much help on that occasion; nor are they much help in dealing with poverty, environmental disasters and people who are forced to flee and seek refuge elsewhere.

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Jeremy Corbyn … The obvious point is that the claim that Britain has an independent nuclear deterrent must be treated with the utmost caution, if not derision, when what is quite clear is where the technology comes from, the relationship with the mutual defence agreement, the expenditure involved and the testing facilities that are available for Britain to use in the USA.

Dr Lewis: There is a question of independence in terms not of manufacture, but of control. Does the hon. Gentleman accept that it is entirely a matter for the United Kingdom Government whether the deterrent would be fired – as opposed to used – fired in response to a nuclear attack on this country and that the United States could do nothing to prevent that from happening?

Jeremy Corbyn: That is indeed a very good question. I hope that the Minister can assist the hon. Gentleman with the answer, because it is fundamental. …

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Dr Lewis: I do not intend to emulate the right hon. Gentleman [John Spellar] by making as many interventions on him as he made on me, but I will say that I have never regarded him as a naive politician. Nevertheless, if he really thinks that the undercurrent and the real message of the stance taken by the Liberal Democrats on this matter is that they were really in favour of a nuclear deterrent, he should do what I did, although it might disturb his sleep a bit, and watch the rebroadcasting of the Liberal Democrats’ conference debates on this subject, because – believe me – all they were interested in during those debates was getting rid of Trident. One never heard anything mentioned about the positive case for a nuclear deterrent. It was another indirect way of going for unilateralism, because they knew that overt unilateralism would be too unpopular.

Mr Spellar: I always say that MPs and Ministers must be responsible for their own words, but if the hon. Gentleman rereads the debate from the time of the Trident Review he will see clearly that at one stage the Liberal Democrats argued for the use of nuclear-enabled cruise missiles. Apart from being a much more expensive option, that is – as I have already said – a far riskier option. I do not mean "risky" in terms of whether or not that option is a credible deterrent, although that is true as well, but in terms of being a destabilising factor, which could lead to much greater tension and – equally importantly – considerable risk of error.

Dr Lewis: In the spirit of compromise and convergence, can the two of us at least agree that, since the Review of the Trident alternatives, the Liberal Democrat position – sending submarines to sea with no nuclear warheads on them, then waiting for a crisis to arise before sailing them back to port and arming them with nuclear warheads – has to be the most irresponsible fantasy-land thinking in the age of the nuclear deterrent? Furthermore, is it not a shame that no Liberal Democrats are here in Westminster Hall today to defend their decision, or – indeed – to explain it?

Mr Spellar: We can draw a veil now over the incoherence and absence of the Liberal Democrats, and get down to the serious and proper debate – it is certainly a proper debate to have – about Britain’s nuclear posture. It is a debate that my party has engaged in for a considerable number of years, in fact ever since the great post-war Attlee and Bevin Government commissioned Britain’s independent nuclear deterrent, a policy that, I am pleased to say, continues today.

Having said that, none of us should underestimate the weighty issues – both the hon. Members who have already spoken stressed this point – that should weigh heavily on all those who have to make these decisions or arguments. ...

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Mr Spellar: ... the key issue – as Michael Quinlan, the Permanent Secretary at the Ministry of Defence, who is also a committed Christian and someone who has thought very deeply about these issues, has said – is the removal of the risks of war and instability. That is absolutely crucial in all these circumstances, including in the Middle East. That is why it is so important to achieve a two-state solution in Israel-Palestine, although Israel-Palestine is by no means the only source of tension in the Middle East. We are seeing so many conflicts taking place in that unhappy region, and that is without any question of nuclear weapons, although, sadly, chemical weapons has been another issue. The resolution of those conflicts and the creation of a stable and peaceful environment is so important.

In the meantime, notwithstanding that, it is also important that the UK plays its part – indeed, it has played its part more than any other country, as I think the hon. Member for New Forest East mentioned – in reducing the proportion of our nuclear armoury. Significantly, that took place under the defence team that I was a member of in 1997 to 2001, but, to be fair I should say that it has been continued by our successors not only in the Labour Government, but in this Conservative Government as well.

Dr Lewis: This is positively my last intervention on the right hon. Gentleman, although that is perhaps giving a hostage to fortune. Will he confirm that, when we took those unilateral steps of reducing our nuclear warhead stockpiles, there was no similar response from any of the other existing nuclear powers?

Mr Spellar: I think that is right. We had hoped that there would be such a response, but we took that decision in context and reduced to the minimum level necessary to maintain effective deterrence. We have reduced the explosive power of our British deterrent by some 75% since that time. That gives us good credentials and bona fides in those discussions. ...

[For Julian's speech in this debate click here.]