In her new book, Mrs McCann opens up about the anguish she and husband, Gerry, felt when three-year-old Madeleine was abducted in 2007, and the desperate search for their daughter that has so far yielded nothing.
The 43-year-old devout Catholic admits to feeling like God had abandoned her and wondering why the prayers for her daughter's return seem to have gone unanswered.
"I am often asked, 'Has your faith been tested? Do you get angry with God?'
"There have been many times when I've felt God has deserted me or that he has let Madeleine down.
"I've occasionally doubted his existence altogether. And yes, I've been angry with Him.
"I've shouted out loud and on occasion I've hit things. I'm afraid even the church pews have had the odd thumping."
Elsewhere in the book, Mrs McCann speaks of being "weighed down by guilt" in the years since her daughters disappearance and the fight she and Gerry faced to keep their marriage together.
Despite her moments of anger towards God, Mrs McCann goes on to say that she does not blame God for Madeleine's abduction.
"The abductor is responsible for that. What I do wrestle with though, is the inexplicable fact that despite so many prayers, almost total global awareness, and a vast amount of hard work, we still do not have an answer.
"My aunt quotes a saying, 'Pray as if everything depends on God. Work as if everything depends on you', and I truly believe that is what we've done.
"Thousands of other people, maybe millions, have prayed. So if Madeleine is alive, why hasn't God brought her back to us?
"If she is not, surely he could lead us to the truth and put a stop to the terrible anguish of not knowing?
"What do we have to do, how long do we have to wait, until he tells us something? Anything?"
She goes on to say that, for now, her anger towards God "seems to have subsided" and that she still believes in him.
"I believe in him and I still feel his presence," she says in the book.
She goes on to say: "For the most part I try my best to accept that it is not for me to question his plan. Maybe I just need to be patient and trust him.
"There is one thing of which I am confident: I believe wherever Madeleine is, God is with her. And in my calmer moments, I also believe that in God's time we'll get there."
'Madeleine' by Kate McCann is out tomorrow, the day of Madeleine's eighth birthday.