THE Tories have failed to make the case for the renewal of Trident, shadow defence secretary Emily Thornberry said yesterday before a once-in-a-generation vote on Britain’s nuclear weapons.

The government is fully signed-up to the replacement of four nuclear submarines despite the costs soaring to a staggering £205 billion.

David Cameron is expected to put the decision to Parliament this summer in a bid to reunite his party after the fractious EU referendum campaign.

But Ms Thornberry told defence experts that there is a “disturbing silence” over key questions about renewal, such as the cost, how long it will take to deliver and whether it will still be an effective deterrent in 30 years’ time.

Speaking at the Royal United Services Institute, she said: “Let’s look at the money. The latest in a series of rapidly escalating estimates in the past year puts the cost of manufacturing the submarines alone at up to £41bn.

“On the costs of the warhead, maintenance and associated infrastructure, there is only silence.”

The Ministry of Defence has refused to answer opposition questions about the cost, claiming that they need “a safe space away from public gaze” to consider their options “unfettered from public comment,” she revealed.

CND general secretary Kate Hudson suggested the government has a “deliberate strategy to avoid giving honest answers about Trident.”

“They know that if more people knew the facts about Trident many, including Conservative MPs, would be outraged,” she said.

Ms Thornberry went on to accuse the government of “deserting” Britain’s obligation to the nuclear Non-Proliferation Treaty signed by former Labour PM Harold Wilson in 1968 and said there was growing frustration internationally at the “inertia” towards multilateral nuclear disarmament.

The Islington South MP, who is leading Labour’s defence review, also challenged the belief that historic party figures such as Nye Bevan had supported Britain possessing nuclear weapons.

She quoted him as saying: “It is not a question of who is in favour of the bomb, but a question of what is the most effective way of getting the damn thing destroyed.”

“Six decades on, what would Bevan make of the fact that the bombs are still with us, now in more countries than ever?” Ms Thornberry asked.