Rowan Williams said it would leave the UK "dangerously dependent on the financial services industry," suggesting the state would become "an offshore financial facility."
The chairman of Christian Aid also appeared to blame the ongoing debate over Europe on a growing sense of nationalism in the UK, he said: "With the Scottish independence agitation and all the questions about a federal UK quite a lot of people feel we need to affirm now what we are, what we distinctively are as English even more than British and that imperceptibly I think strengthens some of this unease about that mysterious entity called Europe which is over there."
In an interview with the Church of Ireland Gazette, he also blamed negative attitudes towards the EU on recent European human rights judgments which he supported, saying: "The fact is, of course, we have absorbed the European Convention on Human Rights into British law anyway, so it is not as if there is some sinister global tyranny forcing us, he said.
"There aren't any sanctions anyway which the European Court of Human Rights can apply.
"They can only state that such and such a decision is 'incompatible'; they can't do anything about it.
"But that has been misrepresented, I think, quite dramatically."