Archbishop Bernardito Auza told a UN session on nuclear weapons the 'incalculable and indiscriminate humanitarian consequences of such weapons' made their use 'clearly against international humanitarian law'.
The meeting was intended to review the progress towards all countries in the world being free of nuclear weapons.
"Despite some progress, nuclear disarmament is currently in crisis. The institutions that are supposed to move this process forward have been blocked for years," the archbishop said.
He added: "Nuclear power countries not only have not disarmed but are also modernizing their nuclear arsenals."
Britain is expected to renew its nuclear weapons programme after the election with Labour, the Conservatives and Liberal Democrats all in favour of maintaining a nuclear deterrent.
Currently the UK has four submarines armed with war heads based on the Clyde on the outskirts of Glasgow.
Archbishop Auza said: "Nuclear weapons cannot create for us a stable and secure world. Peace and international stability cannot be founded on mutually assured destruction or on the threat of total destruction.
"Arguing for nuclear abolition from the moral perspective, the Holy See appeals to human consciences.
"As Paul VI affirmed in his 1965 Address to the United Nations General Assembly, 'Today, as never before, in an era marked by such human progress, there is need for an appeal to the moral conscience of man. For the danger comes, not from progress, nor from science... The real danger comes from man himself, who has at his disposal ever more powerful instruments, which can be used as well for destruction as for the loftiest conquests.'"