THE COST of renewing Britain’s cold-war nuclear submarines could spiral past £40 billion, David Cameron revealed yesterday.

The government originally estimated the cost of replacing Britain’s four Trident submarines would set back taxpayers £25bn.

But manufacturing costs have now been revised up to at least £31bn, according to the Prime Minister’s defence review.

And the government has set aside a further £10bn as a “contingency” fund in case it blows the original budget.

“The revised cost and schedule reflect the greater understanding we now have about the detailed design of the submarines and their manufacture,” the defence review document states.

The nuclear weapons spending boom comes just two days before Chancellor George Osborne is expected to announce 30 per cent cuts to some public services.

The estimate does not even take into account the cost of servicing the submarines throughout their lifetime.

Tory MP Crispin Blunt, chair of the Commons foreign affairs committee, said last month that the total cost of servicing Trident would be £142bn.

Campaign for Nuclear Disarmament general secretary Kate Hudson said: “This is outrageous — the government has completely lost control of the budget.

“With the cost of new submarines rising by 60 per cent to £41bn — and in addition to the £142bn in-service costs reported by Crispin Blunt MP last month — Trident replacement could now rise to a staggering £183bn.”

“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 forces and tackling the real security threats we face, such as terrorism, cyber warfare and climate change.”

The defence review only commits the government to hold a debate on the “principle of continuous at-sea deterrence” rather than a vote.

A Downing Street spokeswoman also refused to pledge a vote yesterday, committing only to a debate.

Responding to outrage in the Commons, the PM promised: “Obviously at the appropriate moment, we’ll want to have a vote in this house.”

Despite the growing threat of terror attacks, Mr Cameron insisted Britain still faced “state-based threats” and insisted that Trident was “our ultimate insurance policy as a nation.”

His claim will be challenged today in a debate in Parliament on Trident renewal called by the SNP.

SNP Defence spokesman Brendan O’Hara MP said the Paris terror attacks showed “the threat to the UK isn’t from an expansionist rival nation state” but comes from terrorists.

“The simplest question to ask ourselves and the most difficult to answer is, in those circumstances, who will those Trident missiles be aimed at,” he said.

The Prime Minister also announced billions will be spent on two new 5,000-strong army “strike brigades,” a 10-year extension to the operational lifespan of the RAF’s Typhoon jets and new equipment for the SAS.

But the government announced plans to axe 30 per cent of the Ministry of Defence’s civil staff over the next five years.