Cardinal Keith O'Brien says the moral case against nuclear weapons is simple
One of the UK's most senior Roman Catholics has criticised plans to renew Britain's nuclear deterrent, calling the retention of Trident "immoral".
Cardinal Keith O'Brien, the leader of Scotland's Catholics, said retaining any nuclear weapons, with the threat to use them, even in defence, was wrong.
The Iraq invasion had been undermined by the UK having its own WMDs, he said.
The government maintains a nuclear arsenal is vital because of the spread of nuclear technology around the world.
The Cardinal, who is spiritual leader to an estimated 660,000 Catholics, said in the Times newspaper that the moral issues around nuclear weapons must not be overshadowed by issues of diplomacy or finance.
Labelling the moral case as "quite simple", Archbishop O'Brien said the use of nuclear weapons was wrong in all cases, and that it therefore followed that retaining them, with the threat to use them if necessary, was also unacceptable.
He went on to say that any "first use" of nuclear weapons would be a crime against God and humanity, and that retaliation by a country which involved an exchange of weapons could not be justified by arguments of defence, but would rather be motivated by vengeance.
The UK currently has four nuclear submarines carrying the Trident nuclear warheads.
The system of missiles, warheads and submarines is ageing, and the government has announced it will be replaced at a cost of £20bn.
Supporters say it is essential that the UK retains an independent nuclear deterrent, but some retired military officers have called for it to be scrapped.
In January, Field Marshal Lord Bramall and Generals Lord Ramsbotham and Sir Hugh Beach all denounced Trident as "irrelevant".
In his article Cardinal O'Brien said that possessing such weapons undermined Britain's moral authority, and that the invasion of Iraq, based on the hunt for weapons of mass destruction, had been undermined by the UK's ownership of its own nuclear WMDs.