The age of coalition government is killing off Trident

Coalition has delayed the renewal of Trident for the last five years and it's likely to do it again for the next five.

Plaid Cymru, the Greens and the SNP are all clearly mulling their red lines in the event of a rainbow coalition with Labour. The Welsh nationalists have used an opposition day debate on the nuclear weapons system this week to make it pretty clear Trident is one of them.

Plaid MP Hywel Williams said:

"Plaid Cymru's opposition to Trident renewal is longstanding and unconditional.

"Fairness and social justice lie at the heart of what our party stands for – these principles could never be upheld if we believed that wasting billions on a Cold War relic at a time when public services are being slashed was in any way acceptable.

"With our anti-austerity alliance likely to hold the balance of power at the general election in May, this is a crucial debate that could influence the political landscape after polling day on May 7th."

Any Plaid involvement in a rainbow coalition would evidently mean another half decade delay on renewing Britain's nuclear deterrent. If Labour go into coalition with the Lib Dems, the project may go through but with three submarines rather than four. That could prove attractive to Labour as it tries to come to a position which is tolerable to its most prominent figures and its rank-and-file. But it's just as likely that the two parties would elect to kick the issue into the long grass for another five years. After all, the current submarines have a life expectancy which takes them into the 2020s.

Trident could prove impossible to renew without a Labour or Tory majority

If it won a majority, Labour would almost certainly join the Tories in signing up for the £25 billion deal in 2016. The party's most prominent figures are still haunted by that dramatic defeat of 1983, when it was almost reduced to third place on what was seen as a far-left manifesto.

But public opinion on the nuclear deterrent has changed significantly since the Cold War. A Mail on Sunday poll after the general election showed 63% supported scrapping Trident. By last year a Guardian poll put it at 79%.

Without a majority it’s hard to see how either the Tories or Labour will ever renew Trident. Tory ministers have pre-empted the Trident decision by spending millions on the Atomic Weapons Establishment in Berkshire, but they remain unable to push ahead with renewal.

This period of stasis coincides with two arguments which make Trident renewal a much harder sell.

Public support for Trident is low, but ministers are intent on renewal

On the one hand, the military challenges Britain faces are of the exact opposite nature to what Trident offers. They are often by non-state actors whose strength lies in their ability to melt into the landscape or conduct asymmetric warfare against far more technologically advanced forces. The demand is for a flexible, nimble response from the military, not the creaking apocalypse of nuclear weapons.

Secondly, austerity has cast the costs of Trident into stark relief. The weapon is set to cost £100 billion over its lifetime. The Tories have tried to rubbish the financial angle. Then-defence secretary Philip Hammond said downgrading from four nuclear submarines to three would save just 0.17% of the annual defence budget. David Cameron said the cost of Trident was less than 1.5% of our annual benefits bill. But whichever way you look at it, it is a costly toy, which does not seem to suit the challenges the UK faces and is considered morally abysmal by much of the public.

The delays forced on Trident by an era of coalition government could prove fatal. With increased public opposition and a growing sense that it is an expensive military solution for another time, Britain's nuclear deterrent could become politically untenable by the time it becomes politically possible.