Trident submarine
One of the Trident submarine fleet carrying nuclear weaponsGetty

The Scottish National Party (SNP) has been given a considerable boost in its mission to oppose the renewal of UK's nuclear deterrent, Trident. The overall cost of replacing and maintaining the system could hit a staggering £167bn ($256bn), according to Reuters.

The figure, calculated by using fresh House of Commons figures and taking into consideration the government's commitment to a 2% of GDP per year spend on defence, is significant because it is much more than previously estimated.

The nationalists expectedly seized on the data and told Reuters that it would be "unthinkable and indefensible" to renew Trident around the 2020s as the UK government continues its cuts to public sector services. But even Crispin Blunt, the Conservative chair of the Foreign Affairs Committee, told the news agency that a renewal would be "too high to be rational or sensible".

"The successor Trident program is going to consume more than double the proportion of the defence budget of its predecessor ... The price required, both from the UK taxpayer and our conventional forces, is now too high to be rational or sensible," he said.

The new figure adds to the varying estimates around the renewal of Trident. A 2006 paper from the Ministry of Defence claimed a successor programme could be as low as £15bn, while Royal United Services Institute (Rusi) has said it would cost up to £80bn and the Campaign for Nuclear Disarmament (CND) claim the deterrent would total £100bn.

The data is also helpful to Jeremy Corbyn, the newly-elected vice-president of CND, but the Labour leader still faces a spilt at the top of his party over the issue. His Shadow Foreign Secretary Hillary Benn, supports the renewal of Trident and a vote on the deterrent was kicked into the long grass at Labour's annual conference in Brighton.

Meanwhile, Shadow Defence Secretary Maria Eagle is still carrying out her review into the policy. But Labour may be pressed into making a decision as the SNP's Westminster leader, Angus Robertson, promised to hold an "early debate" in the House of Commons on the issue.