Heidi Klum feels ''more comfortable'' when she is naked.

The 44-year-old supermodel has revealed she feels happier when she strips down to just her bare body rather than when is covered up with clothes, and she believes her carefree attitude makes her a ''hippie at heart''.

The blonde-haired beauty - who has Helene, 13, Lou, seven, Henry, 11, Johan, 10 - said: ''I feel more comfortable when I'm naked than when I have clothes on.

''I feel more confident now than I was in my 20s. I've had four children, I've learned so many things, I feel like I have both feet on the ground and I feel good in my skin, so I don't mind showing it.''

And the fashion muse has ''always'' found gracing the runway in a skimpy underwear set ''easier'' than modelling a gown or full-length jumpsuit.

The entrepreneur - who launched her eponymous underwear range Heidi Klum Intimates in 2015 - explained: ''Walking on the runway in lingerie was always easier than doing a show with Zac Posen in a jumpsuit and heels where you have to go out and be all cool. My parents have always been very free as well, maybe I'm just a hippie at heart.''

And the catwalk icon will happily walk around her home in the nude on a ''beautiful sunny day'' to ensure she doesn't get tan lines, and she will willingly whip off her bikini top when she is on the beach.

The star said: ''It's not like if you come to my house, I'll be walking around naked. But if it's a beautiful, sunny day and I'm in my backyard and there's no one there? Hell yeah I'm going to take my clothes off. I'd much rather sunbathe naked instead of getting tan lines.

''If I'm on a beach and it's very remote and there are no tourists in sight, then that top is coming off, I've always been a top-optional kind of girl ... I'm not [going topless] because I want to show everyone my boobies, I just didn't know anyone was watching. I'm still discreet in that sense.''

Heidi has recently launched her coffee table book titled 'Heidi Klum By Rankin', which features all nude photographs shot by the iconic photographer John Rankin Waddell over the years, and although she has often been asked to pose bare for photoshoots, she would only do so when John was on set, because he makes her feel ''free'' and captures the natural form beautifully.

She told PEOPLE: ''A lot of people ask you to do nudes in the industry, but I never really did them with anyone else. I've known him for 14, or 15 years now which is longer than I've had children! I felt very free doing those pictures with him, they were always very art-y. I think nudes are beautiful and I love celebrating women's bodies.''