The singer – who has a two-year-old son, Max, with her music producer husband Jordan Bratman – likes nothing better than flicking through an X-rated novel while she is soaking in soapy suds.

She said: "I love water-eroticas – waterproof books full of erotic stories, if you will. You can literally get the book wet, read it in the bath."

The 29-year-old pop star insists Max is the couple's priority, but recognises it's important she and Jordan make time for each other both in public and in the bedroom.

She added to Britain's OK! magazine: "We make sure we have mommy and daddy nights out. Our child comes first, obviously, but there are certain things you can do. Once we know he's in good hands, we go out late at night and have a few drinks. Then we'll come home, dim the lights and do our thing!"

Christina previously vowed motherhood wouldn't stop her enjoying "naked Sundays" with Jordan.

She said: "When it comes to things like our cosy naked Sundays I think it's important for Jordan and I not to lose ourselves. Of course, having a child requires a lot of time and attention, but we think it's really important to still have mommy and daddy time."