A government review of the UK’s defence spending has revealed that the anticipated costs of replacing Trident could rise to £40bn from earlier projections of £25bn.
The Ministry of Defence now estimates that the cost of updating Britain’s ageing fleet of submarines for its independent nuclear deterrent is likely to be £31bn over the course of a 20-year procurement programme.
A further £10bn in "contingency" has been set aside to deal with unexpected cost increases due to the complexity of the project.
The announcement forms part of the Strategic Defence and Security Review, in which Prime Minister David Cameron has set out plans to spend £178bn on buying and maintaining military equipment over the next decade.
He has already announced £12bn to fund a new fleet of maritime patrol aircraft and the creation of two new rapid-reaction "strike brigades".
Cameron has said that MPs will be able to vote on whether to press ahead with the Trident replacement programme, but has not given a firm date.
"Our Armed Forces, police and security and intelligence services are the pride of our country,” he said.
“They are the finest in the world and this Government will ensure they stay that way. Using our renewed economic strength, we will help them keep us safe for generations to come."
Labour leader Jeremy Corbyn told MPs that Britain "does need strong military and security forces to keep us safe", but said his party's own defence review would "recognise that security is about much more than defence".
Despite the sizable increase in the cost of sourcing replacements for the Trident programme, last month the Scottish National Party (SNP) attacked the estimates saying it would cost four times the projected amount.
The SNP said that with an in-service date of 2028 and a missile extension until 2060 the total cost would amount to £167bn.
Following yesterday’s defence spending review, the Campaign for Nuclear Disarmament (CND) announced that it believed the programme could cost even more, at £183bn.
"This is outrageous. The Government has completely lost control of the budget,” said Kate Hudson, CND general secretary.
"In its determination to replace this Cold War relic, the Government is prepared to keep on spending, even if it's to the detriment of conventional tackling of the real security threats we face, such as terrorism, cyber warfare and climate change."