Dr Julian Lewis rose –

Angus Robertson: On the basis of the hon. Gentleman’s long-standing and principled support for nuclear weapons, I would be pleased to take an intervention.

Dr Lewis: In return, I acknowledge the seriousness of the hon. Gentleman’s point about not finding anybody prepared to kill millions of people, but the logical conclusion of that standpoint is that we remain pacifists – [Interruption.] Let me explain. It would mean we could never declare war on any country, whatever the circumstances, because when we do, millions of people inevitably die. The question is, therefore: how do we prevent war? We do it by showing someone that they cannot attack us with these weapons without suffering similar retaliation.

Angus Robertson: I like the hon. Gentleman a great deal, but I note that even he, one of the leading supporters of nuclear weapons, could not give an example of circumstances where he would be prepared to see the killing of hundreds of millions of people. ...

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Dr Lewis: While the Secretary of State is dealing with the Liberal Democrats – only two of whom I see in the Chamber today – will he confirm that a policy of sending unarmed submarines to sea and waiting for a crisis to arise, then sending them back to port to be rearmed while the enemy stands idly by, is actually more dangerous than a policy of keeping them in port all along? Will he also confirm that there will never again be a deal between the Conservatives and the Liberal Democrats to delay the main gate decision, as there was in 2010? That is something with which he had nothing to do, but which should never have been allowed to happen.

The Secretary of State for Defence (Michael Fallon): Let me assure my hon. Friend, in response to his first point, that we are not planning to make future deals of any kind with the Liberal Democrats. On the contrary, we hope to be returned in May with an absolute majority that will restore defence policy to the hands of a Conservative Government. As for my hon. Friend’s first point, he is entirely right to draw attention to the absurdity of an unarmed submarine, perhaps several hundred miles from its base, asking our enemies to hold off for a time while it returns to be kitted out with missiles before heading off on patrol again. That is an absurd policy, and we rather look forward to hearing the Liberal Democrat spokesman try to justify it.

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Sir Gerald Howarth: The right hon. Lady [Dame Joan Ruddock] says that most of the world has moved on. Has she had any intimation from President Putin that the Russians have any intention of engaging in discussions with her about nuclear disarmament? Has she heard from the North Koreans that they intend to abandon their nuclear capability? How does she respond to my right hon. Friend the Secretary of State’s comment that we have reduced our capability and it has made not one jot of difference to those other nations with nuclear weapons?

Dame Joan Ruddock: The hon. Gentleman is citing countries that are of course the minority – the nuclear-armed states. They all have the same attitude as him: they all have Cold War thinking. Many of them have reduced their nuclear arsenals, but they remain more dangerous today.

Dr Lewis: I will try to deal with this in the same theoretical terms as the right hon. Lady is trying to do. If her argument is that we have moved on from the Cold War – it must be noted that at the height of the Cold War she, as the head of CND, wanted us unilaterally to disarm – the point is that there can be no guarantee that we will not move back into a Cold War or face some other threat. We cannot know what threats will arise over the next 30 to 50 years, which is why we need an array of deterrent weapons.

Dame Joan Ruddock: The hon. Gentleman says we cannot know what will happen in the future, but we have a pretty good idea. The threats that were part of the Cold War scenario are very different from those we face today.

Dr Lewis: Tomorrow?

Dame Joan Ruddock: As I go on in my speech, I hope to indicate that I am talking about today and tomorrow. ...

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Dr Lewis: As always, the right hon. Lady [Dame Joan Ruddock] is enormously courteous in giving way. It was discovered after the event that the Russians had been massively cheating on the 1972 Biological Weapons Treaty. Therefore, it is the assurance of the underlying deterrent against other weapons of mass destruction that we have to worry about and be concerned with.

Dame Joan Ruddock: I am afraid that the hon. Gentleman does not make a coherent case. Chemical weapons have certainly been used in recent times – we do not know whether biological weapons have been used – which means that nuclear weapons did not act as a deterrent, so his argument is not sound. ...

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Oliver Colvile: ... As my right hon. Friend the Secretary of State for Defence has repeatedly said, such an approach would mean that we would have only a part-time deterrent. We would depend on a part-time enemy. No doubt we could also go on holiday all the time.

Dr Lewis: May I commend to my hon. Friend and the whole House the lyrics of a song that was prevalent at the Liberal Democrats’ last conference, which came from their own side? Sadly, I have not committed all the verses to memory, but they were wonderful, and the chorus was: "We believe in a part-time submarine". It was sung to the tune of "Yellow Submarine", made famous by the Beatles.

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Dr Lewis: The hon. Gentleman [Roger Godsiff], as always, is being very thoughtful on the subject. What he has said is true: the missile bodies are from a common pool that we share with the Americans. What makes a weapon system independent is not who manufactures it, and not who co-owns it – it is who is in a position to launch it if the need arises. There would be an enormous lead-time to any withdrawal of the sort of co-operation that we need from America, so if there were any attempt at a surprise attack on the UK, because America does not have its finger on our nuclear trigger, the independent system is exactly that.

Mr Godsiff: The hon. Gentleman is knowledgeable about defence issues, but he will recognise that one of NATO’s founding beliefs was, and still is, that an attack on one is an attack on all. The view that the country could be subject to a nuclear attack without the response of the American nuclear umbrella is, in my opinion, inconceivable, and is completely contrary to what NATO is and why it has been successful. ...

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Sir Nick Harvey: ... If one casts one’s mind back to 1980, one will see that our conventional defences were very much greater than they are today. The scale of the nuclear deterrent that we mounted at that time was a relatively small proportion of a large defence, but what we are considering now, as we look forward to the next 30 or 40 years, is a much greater proportion of a much smaller defence because of the succession of cuts that have been made since then.

Dr Lewis: The hon. Gentleman says that we can look forward in anticipation of certain types of dangers but that there is no known nuclear threat. May I remind him of how suddenly the crisis in Ukraine blew up; if it were to develop, as it could, into all-out war that then spilled over into Lithuania or Poland, which are NATO members, nuclear deterrents might become very relevant indeed, very quickly.

Sir Nick Harvey: I will come on to talk about the implications and the consequences of using nuclear weapons, but – although the hon. Gentleman is right to say that the security situation in and around Ukraine deteriorated rapidly – I do not accept for one moment that anything that has happened there makes the prospect of nuclear conflict between ourselves and Russia any more likely than it was before all that started. ...

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Dr  Lewis: The hon. Gentleman [Sir Nick Harvey] is being terribly generous in giving way. The fact is that his party’s policy, strange though it is, is to build another two Trident submarines, however they are deployed. Does it not follow logically, given the terms of the motion, that the hon. Gentleman and his party should vote with us against it?

Sir Nick Harvey: No, because that would imply that we were in favour of a full-scale, like-for-like replacement of the Trident programme. [Interruption.] If one is going to be pedantic, the motion refers to a missile system that is not due for replacement for some years. In fact, what needs to be decided in the next year or so is whether we shall build new submarines. I think we should, but if we make such an investment, it is essential that the submarines are capable of performing other functions. I do not believe that it makes any sense whatever for us to sail the high seas 24/7, waving weapons of mass destruction at the rest of the world, because we thought it was necessary in 1980 or because we would be left looking embarrassed if we did not make that £30 billion investment. ...

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Dr Lewis: Does the hon. Gentleman [Sir Nick Harvey] recognise that although the British deterrent is used all the time to deter, the only scenario in which it is conceivable that it would be fired would be in retaliation for someone having fired a nuclear salvo against us? Therefore, all the [environmental] consequences that he mentions would already have happened, and the only question would be whether it would be worthwhile replying under those terrible circumstances. The purpose is to prevent anyone firing the weapons in the first place, and that is how we avoid the environmental consequences.

Sir Nick Harvey: I am surprised to hear the hon. Gentleman make that case, because I believe he is right. After such a volley had been unleashed against us, no earthly good could possibly be done by firing one back in retaliation, and the more we think our way through that, the more pointless the whole exercise becomes. Indeed, it is not simply pointless, but the rest of the world is becoming increasingly irate about the complacency of those who continue to have these weapons while saying to everybody else: "You’ve got not right to them, but we’re all right, Jack. We’re going to have them." ...

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Dr Lewis: I am greatly enjoying the hon. Gentleman’s [John Woodcock's] speech. Coming back to the real world, is it not the case that the need to have a continuous at-sea deterrent follows directly from the fact that we have a minimum strategic deterrent? We only have four submarines. At any one time only one or two of them can use or fire their missiles – they use them all the time to deter – but the fact is that if we did not have one continuously at sea, a surprise attack would wipe out the whole capacity.

John Woodcock: That is exactly right, which is why a part-time deterrent is no real deterrent at all. The point of having submarines that are continuously at sea means that they are, in effect, completely invulnerable. If, in a future nightmare scenario, the UK was seriously threatened by a nuclear attack, any potential nuclear adversary would know that they could not fire without being fired on. Even if they flattened the UK, they would always face the counter-strike. That is why it is a genuine deterrent and makes a nuclear attack less likely. ...

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Dr Lewis: Does my hon. Friend [Rory Stewart] agree that the whole point of Article 5 of the NATO Treaty is not the question of which of the members of NATO an attacked country will look to to get most military help; rather, it is to take any uncertainty out of the question of who will declare war if a NATO country is attacked? Therefore, if a NATO country is attacked, our existing obligations are to declare war on the attacker. Does that not mean that we must be very careful how widely we extend NATO membership?

Rory Stewart: I agree absolutely, and that is a very important point. This NATO obligation is an unbelievably serious and important obligation. We have stretched it absolutely to its breaking point. If we are going to be serious about it, we have to follow through and that absolutely means we should not be giving guarantees to people we have no intention of protecting. We should not be writing cheques we are not prepared to have cashed. ...

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