Lord Carey told a fringe event at the Conservative Party conference organised by the campaign group Coalition for Marriage, that gay marriage was the first step on the "slippery slope" to polygamous, "Mormon-style" relationships.
He said: "Let's have a sensible debate about this, not call people names," he said. "Let's remember that the Jews in Nazi Germany, what started it all against them was when they started being called names. That was the first stage towards that totalitarian state."
Lord Carey rejected the suggestion that advocates of gay marriage were "bigots" who would not listen to the concerns of religious groups who disagreed.