Lib Dems outline alternatives to Britain's nuclear deterrence programme

The Liberal Democrats have released a document outlining alternatives to the UK’s current Trident nuclear deterrence programme, putting them at odds with their coalition partners and potentially shaping their manifesto for the next election.

Nuclear deterrence rests on the principle that a state or group considering an attack on the UK would have to take into account the possibility of massive retaliation or pre-emptive action in the form of a nuclear strike. At present, the UK has a fleet of four Vanguard submarines, which will reach the end of its lifespan by 2020. The final decision on whether to renew the programme has been delayed until 2016 after the next election.

The Trident Alternatives Review doesn’t make any policy recommendations, but says that there are alternatives to the existing system that could still provide a significant deterrence effect.

With the third and fourth Vanguard submarines due to leave service in 2040, this was the deadline set for the most viable options. The paper says the options open that could meet the deadline, and judged to be most credible and comparable in cost to renewing the current system were: the use of large aircraft with stealthy cruise missiles; fast jet with supersonic cruise missiles; or hunter-killer submarines with stealthy cruise missiles.

Britain could reduce its fleet, but an alternative system like putting nuclear warheads on cruise missiles would be more expensive and potentially reduce whom the UK could deter unilaterally and increase operational complexity.

There are also non-continuous postures including the use of nuclear submarines at reduced readiness when the country deems the threat of attack to be low.

But Conservative defence secretary Philip Hammond said reducing the number of submarines in the fleet would leave the UK vulnerable

Just because we do not perceive an immediate threat today, does not mean there would not be a threat over the 60-year odd time horizon we are looking at. The truth is, at the end of the day, we can have continuous-at-sea nuclear deterrents or we can have a part-time deterrent. The part-time deterrent will save us only trivial sums of money.

And Prime Minister David Cameron said policy will remain unchanged following the review

Government policy remains as set out in the Strategic Defence and Security Review. We will maintain a continuous deterrent and are proceeding with the programme to build a new fleet of ballistic missile submarines. Final decisions on the successor submarines will be taken in 2016.

Here's Hammond and Liberal Democrat MP Sir Nick Harvey on BBC Radio 4 this morning: