Trident missiles are launched from Vanguard class submarines
The UK's nuclear deterrent should be scrapped, according to a group of retired senior military officers.
Field Marshal Lord Bramall and Generals Lord Ramsbotham and Sir Hugh Beach have denounced Trident as "irrelevant".
General Lord Ramsbotham told the BBC that the "huge" £20bn expense of renewal has to be questioned and said the armed forces should get more funds.
Supporters say it is still essential that the UK should maintain its independent nuclear arsenal.
Lord Ramsbotham told the BBC's Newsnight programme: "We argue it is conventional weapons we now need.
"Their pin-point accuracy, their ability to help our forces in the sort of conflicts that are taking place is something which means you have to question the huge expense of Trident, which is limiting what we can do."
In a letter to the Times, the men say the UK is too dependent on the US when it comes to defence.
They write: "Nuclear weapons have shown themselves to be completely useless as a deterrent to the threats and scale of the violence we currently face, or are likely to face - particularly international terrorism."
TRIDENT MISSILE SYSTEM
Missile length: 44ft (13m)
Weight: 130,000lb (58,500kg)
Diameter: 74 inches (1.9m)
Range: More than 4,600 miles (7,400km)
Power plant: Three stage solid propellant rocket
Cost: £16.8m ($29.1m) per missile
Source: Federation of American Scientists
"Our independent deterrent has become virtually irrelevant except in the context of domestic politics.
"Rather than perpetuating Trident, the case is much stronger for funding our armed forces with what they need to meet the commitments actually laid upon them. In the present economic climate it may well prove impossible to afford both."
Traditionally these have been the views of those politically on the left and the Campaign for Nuclear Disarmament.
Kate Hudson, who chairs the group, said: "This statement debunks the myth that nuclear weapons are necessary for our security.
"These generals are no pacifists - they are purely practical about Britain's needs and have concluded that we are better off without them."
The retired officers said the unilateralist case was now the only way forward and rejected arguments that the defence system was essential for a place at the "top table" of the United Nations Security Council.
The Trident system - made up of submarines, missiles and warheads - are due to end their working lives in the 2020s.
Former prime minister Tony Blair gave the go-ahead to replace the system in 2006.
Crossbench peer General Lord Ramsbotham told Newsnight that he and his fellow writers wished to encourage further debate about Trident and what it represented.
He said: "I don't think it is independent. First of all, we don't own the missiles and secondly I think it's absolutely unthinkable that we should consider or even threaten using it without having the clearance of the United States."
But Conservative MP and chairman of the Defence Select Committee, James Arbuthnot, told Newsnight: "It's an awful argument to put that it gives us a place on the Security Council of the United Nations but I think it actually is true.
"When South Africa unilaterally disarmed its nuclear weapons I think it did lose influence."
Former Conservative defence secretary Sir Malcolm Rifkind said he was a "strong believer in multilateral nuclear disarmament" and was presently involved in a campaign to try to get all the nuclear powers to reduce their dependency on such weaponry.
He said the officers' call for "Britain to get rid of all its nuclear weapons regardless" was a "very serious mistake" and unworkable.
He said: "Ultimately we are talking about an insurance policy for the next 50 years.
"Russia and China remain nuclear powers. I don't know who is going to run China 20 years from now, they could be friendly, they could be hostile".