The Quakers have become the latest critics of a service taking place at Westminster Abbey next month to commemorate 50 years of nuclear deterrents in British waters.
The abbey has already come under fire from Church of England bishops and peace campaigners over the service on Friday 3 May.
The service is being hosted by the Royal Navy to mark 50 years of continuous patrols by the UK's nuclear submarines.
The Quakers have written to the Very Rev John Hall, Dean of Westminster Abbey, urging him to reconsider the service.
In the letter, Quakers recording clerk Paul Parker said nuclear weapons were "faithless".
"To threaten humanity and the planet with nuclear annihilation is in our view contrary to what God would have us do," he said.
"It is indeed imperative that we all continue to pray and work for peace throughout the world, but peace is not served by the maintenance, possession and threat of use of nuclear weapons."
Westminster Abbey said the service was being held to "recognise 50 years of continuous at sea deterrent" and "pray for peace throughout the world".
Despite the opposition, the Abbey has not moved to cancel the ceremony.
The Bishop of Colchester, the Rt Rev Roger Morris, and the Bishop of Chelmsford, the Rt Rev Stephen Cottrell, have both said that the ceremony contradicts Church teachings.
Kate Hudson, general secretary of the Campaign for Nuclear Disarmament, said the service was "morally repugnant".
"This sends out a terrible message to the world about our country. It says that here in Britain we celebrate weapons - in a place of worship - that can kill millions of people," she said.
"If the Defence Secretary doesn't cancel this service, we call on the Church authorities to step in to stop it."
The campaign group has vowed to hold protests at Westminster Abbey on the day of the service if it is not cancelled.