Will Britain keep its Trident nuclear program?

British lawmakers will vote Monday on whether to replace the country's fleet of nuclear-armed submarines, an expensive project which Conservative lawmakers say is key to maintaining the country's status as a world power.

With a Conservative majority of 16, Parliament is likely to approve renewing the Scotland-based, nuclear-armed Trident submarines, despite opposition from lawmakers in the Labour Party and the Scottish National Party who say the money would be better spent elsewhere.

According to pre-released quotes issued by her office, newly appointed Prime Minister Theresa May will tell lawmakers that the nuclear threat "has not gone away" and that "if anything, it has increased." 

"It is impossible to say for certain that no extreme threats will emerge in the next 30 or 40 years to threaten our security and way of life," she will say. "We cannot abandon our ultimate safeguard out of misplaced idealism."

Since 1969, a British submarine carrying nuclear weapons has always been on patrol, BBC reports. The submarines provide an insurance that, even if their traditional defense capabilities were destroyed in a nuclear attack, the British would still be able to retaliate.

Parliament agreed in principle in 2007 to renew the system, and Monday's vote is meant to rubber-stamp the decision to build four new submarines. 

Now, some lawmakers say the weapons are no longer needed and would not be effective in defending the country against a threat from terrorists. They also say the project is too expensive: the Ministry of Defence has said that replacing the four aging submarines would cost £31 billion, with a contingency of £10 billion and another £4 billion already allocated to the design process. According to Reuters, the total costs for maintaining the submarines over their expected lifespan of 32 years could reach £167 billion ($220 billion). 

"Money is important, particularly at a time of financial stress," lawmaker Emily Thornberry, defense spokeswoman for the Labour Party, told BBC Radio on Monday. "I think it is reckless for us to plough on ahead with the most expensive of all the various options and there are step-downs we can take."

The project is also opposed by some military officials, who say the money could be better spent on maintaining the army and on more conventional technology, as both have recently suffered cutbacks.

In February, US Defense Secretary Ash Carter stressed the necessity of renewing the submarines, saying that Trident aids the UK's "special relationship" with the US and helps it "continue to play that outsized role on the global stage that it does."

But adversaries of the system worry that the move may worsen, rather than lessen, the potential for danger.

"I believe that a new generation of nukes will not only fail to make Britain more secure, but will increase the dangers we’re facing," wrote Caroline Lucas, sole MP for the Green Party, for the Daily Mirror on Sunday. "Keeping nukes also sends a dangerous signal to the rest of the world that security means owning weapons of mass destruction. At a time of increased tension that's the opposite of what we should be saying."

This report contains material from Reuters and the Associated Press.