The Archbishop of Canterbury has told an interviewer he cannot say whether gay sex is sinful or not.

In an interview with GQ, he told Alastair Campbell, who was spokesman for Tony Blair when he was Prime Minister, that he could not give a 'straight answer' to the question: 'Is gay sex sinful?'

Asked why not, the Archbishop replied: 'Because I don't do blanket condemnation and I haven't got a good answer to the question. I'll be really honest about that. I know I haven't got a good answer to the question. Inherently, within myself, the things that seem to me to be absolutely central are around faithfulness, stability of relationships and loving relationships.'

He agreed that this could be between a man and a man or a woman and a woman.

But he added: 'I am also aware – a view deeply held by tradition since long before Christianity, within the Jewish tradition – that marriage is understood invariably as being between a man and a woman. Or, in various times, a man and several women, if you go back to the Old Testament. I know that the Church around the world is deeply divided on this in some places, including the Anglicans and other Churches, not just us, and we are – the vast majority of the Church is – deeply against gay sex.'

This meant he was struggling to be faithful to tradition, to the scripture, to understand the will of God in the 21st century and to respond appropriately with an answer for all people, he said.

As the primates or archbishops from the worldwide Anglican Communion meet in Canterbury this week, with boycotts from some conservatives over the issue of homosexuality, Archbishop Welby admitted: 'It is irreconcilable.'

He also condemned homophobia, saying: 'I don't think it is sinful to say that you disagree with gay sex. But to express that by way of hatred for people is absolutely wrong in the same way as misogyny or racism is wrong.'