Mitt Romney says in an interview that one reason he's reluctant to release his tax returns is that it reveals how much money he and his wife have given to the Mormon church.

In an interview with Parade Magazine, Romney says his church doesn't publish how much people tithe. In the interview, to be published Sunday, Romney says he never intended for his donations to become public.

Democrats have hammered the Republican presidential candidate for refusing to release any tax returns beyond his release of his 2010 return and a summary of last year's tax information. He has said he plans to release his full 2011 return before the Nov. 6 election.

Romney hasn't previously mentioned his reluctance to reveal charitable donations as a rationale for keeping his taxes private.