Lord Carey has said the couple should marry in a small church

On Sunday, Lord Carey told BBC One's Breakfast With Frost programme while it is their decision he likes to think "at some point they will take the plunge".

Press reports have said the couple are unhappy that Lord Carey has commented on their relationship in his new book.

He also suggested the couple would choose a simple church service rather than a ceremony at Westminster Abbey.

"I think that is probably what they will prefer when that decision is made," Lord Carey told the BBC.

'Special role'

When he becomes monarch the Prince of Wales would inherit the post of the Supreme Governor of the Church of England.

New rules mean the prince could marry Mrs Parker Bowles in church

But Lord Carey said it was "absolutely right" that the prince should be married as "the present position is eventually unsustainable".

He rejected reports that he had apologised to Mrs Parker Bowles over the headlines his book has generated.

"I hope Camilla is not distressed. She is a friend.

"I have written a letter to her and if there are apologies to be made, I will make them, of course, but I don't think there are," Lord Carey said.

He went on to say: "How can I, as a Christian leader, want to move away from a commitment to marriage and the fact that the monarchy has a very special role in our nation?

"They exemplify our standards and values and that is what I am trying to get across."