David Cameron launched a defence of Britain’s Trident deterrent on Thursday, saying it would be foolish to scrap Britain’s fleet of nuclear submarines while countries like Iran and North Korea seek to develop their own atomic weapons.

The coalition partners appear to be on collision course over Trident.

The Conservatives want a like-for-like replacement for the current fleet of four Vanguard-class submarines when they reach the end of their operational lifespan in the 2020s.

The Lib Dems want a cheaper alternative, which could include extending the lifespan of the current subs, switching Trident missiles to other submarines or using cruise missiles instead of long-range ballistic missiles.

Labour is committed to having a nuclear deterrent but wants to keep a close eye on the costs.

The Scottish National Party (SNP) is unique in that it wants to evict the Vanguard fleet from its home at the Faslane naval base near Glasgow.

Trident is likely to be an explosive issue in the run-up to next year’s referendum on Scottish independence. Let’s see if we can blast through some of the hype.

“Our current nuclear weapons capability costs on average around 5-6 per cent of the current defence budget. That is less than 1.5 per cent of our annual benefits bill.”
David Cameron, 04 April 2013

That percentage of the defence budget (£37bn) comes out at about £2bn a year, which fits in with independent estimates of the annual cost of running Trident.

It’s not clear whether the Prime Minister is including the cost of upgrading the project in his total, but it seems unlikely.

Estimates of the one-0ff costs of replacing Trident range from £20bn to more than £30bn over 30 years.

Add that to an assumed annual running cost of £2bn and you come very close to the total calculated by Greenpeace in 2009: £97bn over 30 years. But estimates of the long-term costs of big capital spends are notoriously hard to get right.

The current annual spend on Trident is less than 1 per cent of the current benefits bill, depending on how you look at it. We are due to spend around £200bn this year on welfare, if you lump state pensions, benefits and tax credits togther.

On the other hand, 6 per cent of the defence budget is double the percentage admitted to by ministers in the early days of Trident, and £2bn a year would pay the salaries of nearly 100,000 new nurses, and so on…

“This jobs bogeyman is brought out routinely…only 520 jobs are directly related to Trident.”
Jamie Hepburn, SNP MSP for Cumbernauld and Kilsyth, 04 April 2013

Estimates of potential job losses if Trident leaves Scotland have ranged from 520 to 19,000.

The lower figure comes from a freedom of information request by the Scottish branch of the Campaign for Nuclear Disarmament. The Ministry of Defence said there were only 520 civilian jobs directly reliant on Trident in the whole of Scotland.

But the MoD told us that number doesn’t give a true picture of the situation. It leaves out military personnel as well as “the vast majority of jobs at Faslane which support the deterrent, the Vanguard submarines and the infrastructure which keeps the deterrent operational”.

The government says there are 6,500 military and civilian jobs at Faslane, and this figure will increase to over 8,000 by 2022. Labour has said an additional 11,000 jobs are directly or indirectly reliant on the base, giving a total of 19,000 jobs at risk if it closes – a figure disputed by local trade unionists.

Not all those 8,000 people will work on Trident, although it seems likely that the real number of people whose livelihoods depend on maintaining the Vanguard submarine fleet must be greater than 520.

In a sense, who does and doesn’t work on Trident is arguably something of a red herring. The real question for the SNP is how many other jobs outside the immediate Trident workforce would be at risk in the event of independence.

The nationalists say Scotland would be able to carry on building warships and could continue to supply the United Kingdom, safeguarding local jobs.

That was flatly contradicted by the House of Commons Scottish affairs committee, whose recent report concluded that Scotland’s shipyards “are doomed” if the country leaves the UK.

The British government hasn’t built a warship outside the UK for 200 years, according to ministers who gave evidence, and is unlikely to dish out contracts to an independent Scotland.

A Scottish navy might need to build ships, but it might inherit all the vessels it needs from the Royal Navy. And the total size of a new navy would only be around 2,000 personnel, according to former SNP defence spokesman Stuart Crawford’s influential analysis.

Expert opinion differed as to whether the shipyards could realistically build and sell equipment to foreign clients. It’s fair to say that a big question mark hangs over this option.

The Labour, Conservative and Lib Dem MPs who signed off the report said: “We believe the Scottish government now must clarify exactly what alternatives it intends to put in place to safeguard the jobs of the thousands of workers involved in this industry and these local economies.”

By Patrick Worrall