The Reverend Ksawery Knotz has a message for all married Catholic couples out there: there's nothing wrong with a steamy sex life.

In fact, it's a good thing.

In his new book Sex As You Don't Know It: For Married Couples Who Love God, the Polish friar provides a theological and practical guide for Catholics that has little in common with the strait-laced attitudes often associated with the Roman Catholic Church.

'Some people, when they hear about the holiness of married sex, immediately imagine that such sex has to be deprived of joy, frivolous play, fantasy and attractive positions,' Knotz writes.

'(They think) it has to be sad like a traditional church hymn.'