Marilyn Manson has sex a minimum of five times a day in the dark but refuses to take his underwear off in case there's a fire in the house.

The 46-year-old singer insists on the lights being switched off when he is engaging in the act of ''sexual congress'' with his girlfriend, photographer Lindsay Usich, because he is ''shy'' but loves to spend the day in bed with her and they recently set a new record by having sex 10 times in one day.

He said: ''I'm just really shy, despite what you'd imagine. I have a phobia that the house is going to catch fire, and I don't want to be naked.''

The 'Rock is Dead' hitmaker always has his bedroom temperate set at 65 degrees Fahrenheit and insists on having black bed sheets, and, like his bed linen, he loves to wear dark underwear which his 30-year-old girlfriend regularly flashes a UV torch onto to check whether or not he has been unfaithful to her.

Marilyn - who previously dated actresses Rose McGowan and Evan Rachel Wood, porn star Jenna Jameson, and was married to burlesque queen Dita Von Teese for just over a year - added to Rolling Stone magazine: ''I have a blacklight flashlight at home, which will show if sperm is on anything, and Lindsay has used it on my underwear to see if I'd done something naughty when I was out.

''I said, 'Fooled you. I might have changed my underwear. How do you know that I didn't?' She goes, 'Because you don't change your underwear.' I said, 'That is true. Good answer. Good answer.' ''