Is it time for the UK to give up its nukes?

It's quiz time.

Who said this? “We need our nuclear deterrent as much today as we did when a previous British Government embarked on it over six decades ago … The nuclear threat has not gone away."

And who said this? "While the world has changed greatly since the 1980s, the political reality has not: we will appear dangerously weak …if we are prepared to give up [Trident] while the world remains so unstable."

Not much difference, is there? The first was David Cameron, writing in the Daily Telegraph yesterday, and the second was the Labour frontbencher Angela Smith and a former aide to Gordon Brown, John Woodcock, writing jointly in last Monday's Guardian.

So our two major political parties still agree, as they have done for many years, that the UK needs to hang on to its bomb. (Funny, isn't it, that when we have it, it's an "independent nuclear deterrent", but when someone we don't approve of has it, or threatens to acquire it, it becomes a "weapon of mass destruction.")

Has nothing changed, then, since Nye Bevan argued passionately against unilateral nuclear disarmament at the Labour party conference in 1957, on the grounds that "it would send a British Foreign Secretary naked into the conference-chamber"?

In fact, of course, a great deal has changed. For one thing, Joe Stalin and the Soviet Union have long gone; for another, the main security threats we face have changed beyond recognition. Now, according to the government's Strategic Defence and Security Review published in October 2010, they are terrorism, cyber-attacks and natural disasters, like major flooding and pandemics.

And even though the Review also says that an effective nuclear weapons programme remains "the United Kingdom’s ultimate insurance policy in this age of uncertainty", it is far from clear, at least to me, what our nuclear warheads will be aimed at if we do suffer a cyber-attack or a major pandemic.

I raise these questions, of course, while Western and other governments watch nervously as North Korea goes through another of its periodic bouts of nuclear sabre-rattling. (I wrote about North Korea seven weeks ago, when I suggested "We're not paying enough attention to rising tensions in east Asia" -- so don't say I didn't warn you.)

The prime minister wrote yesterday: "Only the retention of our independent deterrent makes clear to any adversary that the devastating cost of an attack on the UK or its allies will always be far greater than anything it might hope to gain."

I wonder. Any adversary? It didn't deter Argentina when it invaded the Falklands in 1982, did it? Nor did it deter the 7/7 suicide bombers when they attacked London's public transport network in 2005. Nor did the fact that the US possesses the biggest nuclear arsenal on earth stop Osama bin Laden and his comrades from launching the 9/11 attacks in 2001.

So the deterrent argument is, shall we say, arguable. I don't discount it all together, however, because I accept the possibility that, for example, India and Pakistan may be slightly less likely to take up arms against each other, now that they both have nuclear weapons.

What surprises me is that there's been so little discussion about the UK nuclear arsenal in the context of the current public spending debate. We could save billions by scrapping the Trident nuclear missile programme -- or even by not going ahead with a like-for-like replacement -- but the Westminster consensus seems to be that any major party that openly calls for an end to Britain's nuclear bomb programme would lose support at the ballot box.

(In fact, an opinion poll carried out in 2010 for the foreign policy think-tank Chatham House suggested that 50 per cent of UK voters want Trident either scrapped entirely or replaced with something cheaper. So the "it'll-lose-us-sackloads-of-votes" argument may not be as powerful as most politicians seem to think.)

So far, only the Green Party is prepared to say openly what many senior military and defence analysts say privately. Green MP Caroline Lucas stuck her neck out last October: “With the total cost of replacement likely to come in at an eye-watering £100 billion over the next 30 years, can the UK afford such an extravagance? Is a Cold War deterrent really the right solution for our defence needs in the 21st century?"

The Lib Dem view, as set out yesterday by the MP Sir Malcolm Bruce, is more nuanced: "We do accept the case for a nuclear deterrent and we are not in favour of unilateral disarmament. We are saying we shouldn't replace Trident on a like-for-like basis but we are looking at alternative nuclear deterrents once Trident has passed its sell-by date."

An official government review into Trident replacement options is due to be published within the next couple of months. Perhaps that's when we can start to have a proper debate. Has the time come for the UK to give up its nukes as an irrelevant extravagance?

Mind you, if I were a North Korean policy-maker, I would look at what happened to Saddam Hussein and Muammar Gaddafi after they abandoned their nuclear weapons programmes, and I would conclude that I do not intend to make the same mistake they did. But no, I don't put the UK in the same category, because I really don't think we face the remotest threat of hostile military action from either the US or NATO if we renounce our "deterrent".

So how worried should we be about North Korea, as the US and others ramp up their defences in response to the blood-curdling rhetoric from Pyongyang? I'll take my cue from the South Koreans, who don't seem worried at all. And after all, they, of all people, would have the most reason to be worried if the current tensions really did threaten to spill over into war.