The following article was written by Lord William Wallace and published today on the Liberal Democrat Voice Website.

Jeremy Corbyn’s arrival as Labour leader will make it easier for the right-wing, in politics and media, to dismiss all criticism of the decision on replacing Trident that Parliament will make next year as wacky. Yet there are many, within the expert defence community as well as outside, who think that committing a third of the UK’s defence procurement budget, over a decade, to the replacement of a system designed for a contingency that no longer exists, is unjustifiable.

Liberal Democrats in the coalition examined the case for alternatives, against stubborn Conservative opposition. Next week the Liberal Democrat conference will debate what response to give to Conservative determination to press on with a full four-submarine programme, while cutting military spending elsewhere.

Britain’s nuclear deterrent was developed, early in the Cold War, to defend Western Europe – above all West Germany – against Soviet attack. The ‘Moscow criterion’ was essential to its rationale; for an ‘independent’ British deterrent to be credible, in the hypothetical circumstances of American failure to guarantee nuclear retaliation in response to Soviet invasion, Britain alone could destroy the core of the Soviet state. Behind this rationale, the UK independent deterrent was also from the outset about international status: our claim to remain a global power, to be America’s key partner on this side of the Atlantic, to walk taller on the world stage than Germany, France, Italy and other NATO members.

25 years ago the cold war ended, Soviet forces withdrew from central Europe, and the USSR collapsed. With that also collapsed the rationale for maintaining the capability to knock Moscow out in a second strike, guaranteed by four submarines, at least one continuously patrolling at sea. Arguments about status still linger – that our UN Security Council seat would be at risk without Trident, that we would fall behind the French, that Washington would no longer listen to us. No government since 1990 has however provided a new military rationale. A threat from Iran now seems less plausible; an alleged threat from North Korea was never credible.

Our Conservative government has opted out of negotiations with Russia over the future of Ukraine. It talks in unilateralist terms about ‘bombing ISIS’, as if Britain alone remains a key player in the Middle East. It seems determined to deny that Britain is committed to European defence, or to continued political cooperation with our European partners. The size of the army, the working ships of the navy, the air transport needed to support operations in weak and failing states across Africa, are all being cut; but the nuclear deterrent, the badge of Britain’s claim to stand alone in the world, is to be sustained.

Liberal Democrats reject these competing unilateral stances. We hold that Britain’s security can only be maintained in cooperation with our neighbours. We will debate at our Bounremouth conference the threats that Britain and its partners now face, and the spending priorities these imply. The last Security and Defence Review listed terrorism, climate change, state collapse leading to migration, pandemic diseases, and trans-national crime as Tier One threats. Nuclear sabre-rattling from a distant and economically-weak Russia is not a threat to Britain – above all not to a country drifting away from engagement with the European continent. We are committed to common defence, within NATO, rather than posturing about Britain standing alone. And we insist on addressing the opportunity costs that the Conservative government is sweeping aside.

British defence spending is under acute strain. Liberal Democrats, unlike the Conservatives, will address the best way of ensuring that the UK prioritises resources to meet post-cold war threats. There is a case for maintaining a nuclear capability, against the distant prospect of an emerging threat in 10-20 years’ time. The case has not been made for a like-for-like replacement, continuously patrolling under the sea in response to threats and claims to status that were defined before most of the population of Britain today were born.

Lord Wallace of Saltaire is a Liberal Democrat member of the House of Lords.