The government is considering shifting the cost of the Trident nuclear deterrent from the Ministry of Defence budget, the national security adviser Mark Sedwill has disclosed.



The MoD and the Treasury have been at odds since 2007 over who should pay the capital costs of replacing Trident.

In 2007, the MoD said the capital costs of procuring the nuclear deterrent had been borne by the Treasury rather than come from the core defence budget. The Treasury at the time rejected this.

In 2010, the then chancellor George Osborne clashed with then defence secretary Liam Fox. Osborne insisted the costs come out of the defence budget and won.

The issue surfaced again last month when defence secretary Gavin Williamson said the nuclear deterrent “has traditionally not sat as part of the defence budget: that changed only post-2010”.

The MoD issued a correction on 7 December, saying: “To clarify, the UK’s nuclear deterrent has always been funded from the defence budget.”

Sedwill – the civil servant overseeing a review of the UK’s security services including the intelligence agencies, police and military – revealed the potential budget change while being questioned by the cross-party parliamentary national security strategy committee.

Conservative MPs, concerned about what they see as the MoD struggling to meet all its commitments, have mounted a campaign in recent months to have the Trident bill moved out of the department’s budget.

Tory MPs on the committee pressed Sedwill to confirm whether he was proposing to cut MoD assets – such as two ships used for amphibious landings – and reduce the number of marines. Sedwill said only that “adjustments” would have to be made.

The MoD has an annual budget of £36bn. The estimated cost of the Trident programme, mainly four new submarines, is £31bn, with a further £10bn in reserve for extra costs.

Whitehall officials said there was Conservative pressure too for Sedwill’s mini-review to be turned into a full-scale strategic review, in the hope that this would lead to a bigger increase in the defence budget.

Sedwill told the committee his aim was not to cut the existing £56bn spent annually on security but rather to redistribute it across departments where necessary.

Whitehall officials have said the MoD is facing brutal cuts. Taking the cost of Trident out of the MoD budget could help quell a Tory rebellion.

Sedwill told the committee the threat from Russia had worsened since the last strategic defence review in 2015, in particular that posed by cyber-attacks.

He said the UK benefited from having allies: the combined UK, French and German defence budgets were twice the size of Russia’s.

Asked about Williamson’s recent call for Britons who fought for Islamic State to be hunted down and killed, Sedwill opted for a diplomatic answer, saying this did not amount to a change in approach – a call for a greater number of drone strikes – but was part of a range of options, including arrest and trial. Lethal force had been used before and would be used again as necessary, Sedwill said.

A government spokesperson said: “No decisions have been made on any parts of the national security capability review yet.”