The Catholic Bishops of England and Wales have urged the government not to replace Trident nuclear weapons.
The government has yet to make a decision on Trident's replacement
Bishop of Portsmouth Crispian Hollis said if the UK developed a replacement, the aim of international disarmament would be undermined.
He also said it was debatable whether nuclear weapons were actually a deterrent as violence continues around the world despite their presence.
A decision has not yet been taken on whether to replace Trident.
But defence minister Lord Drayson told MPs on Tuesday a "preferred option" would be in a white paper to come by the end of the year.
Bishop Hollis said nuclear weapons could never be used because they were "so uniquely destructive" in that they killed indiscriminately - not just combatants.
"That involves the huge killing of innocent people and that is never right," he told BBC Radio 4's Today programme.
Even though nuclear weapons have not been used in war since World War Two, Bishop Hollis said it was arguable nuclear weapons did not act as a deterrent.
"We've certainly had an escalation of surrogate wars going on throughout the world because of the nuclear presence, but at the same time it hasn't checked the violence."
Tony Blair is thought to favour replacing Trident but has promised a full debate before a decision is made, while Chancellor Gordon Brown has also said he wants to keep Britain's "independent nuclear deterrent".
MPs have been promised a "veto" on replacing Trident - after a full public debate - by Commons leader Jack Straw.
The issue is due to be discussed by Cabinet on Thursday.
Three Cabinet members - Foreign Secretary Margaret Beckett, International Development Secretary Hilary Benn and Northern Ireland Secretary Peter Hain - are said to have concerns about replacing or extending Trident, the Times newspaper reported on Wednesday.
The Conservatives are in favour of maintaining Britain as a nuclear power.
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
Disarmament campaigners say the estimated £25bn needed to replace Trident would be better spent on improving public services and boosting pensions.
The CND said activity at Aldermaston "suggests the decision to go ahead with a new generation of nuclear weapons has already been taken".
Building work, costing £1bn, at the Atomic Weapons Establishment at Aldermaston - and the creation of hundreds of new jobs - have sparked claims of new nuclear developments.
But Lord Drayson said the work was to ensure existing weapons were safe.
Greenpeace has said the international Nuclear Non-proliferation Treaty is being contravened.
Among other issues, the white paper would discuss whether to replace the current submarine-based missiles with a land-based or aircraft-based system, said Lord Drayson.
He said the "defence need" was the main consideration when it came to replacing Trident, rather than the impact on jobs or maintaining the skills base to build nuclear submarines.