Mary-Kate Olsen can't leave the house if she isn't happy with what she's wearing.

The 25-year-old blonde - who runs three successful clothing labels with Twin Sister Ashley - says it's very important for her to be comfortable in the clothes she's got on otherwise she finds it a struggle to go out.

She said: ''I think as soon as you start dressing for someone else, it goes wrong. I can't leave the house if I don't like what I'm wearing. I mean, I literally can't.''

However, Mary-Kate insists she's not obsessed by fashion, saying: ''We're not really fashion obsessed. In fact, I don't know when things are fashionable or not. I'm not very aware of trends or hot new items. We're not cool.''

Mary-Kate also revealed how she and Ashley want to carry on expanding their fashion range and look to Tom Ford for inspiration.

She told Britain's ELLE magazine: ''It's about being creative, but having a bigger vision for that creativity. For a designer to be successful nowadays, they need to know much more than just design. Tom Ford, his career is astonishing - the way he's been able to do everything he has wanted to do and really not compromise at all. From fashion to film, it's such a singular vision.''