Actress Mary-Kate Olsen has hit out at people who question her about the Olsen twins' fortune - insisting her personal wealth is of no concern to the outside world.

The 21-year-old began acting as a baby, appearing in 1980s show Full House alongside twin sister Ashley.

And the pair, who have gone on to launch a hugely lucrative merchandising empire, are estimated to be worth over $100 million.

But when questioned on her position as a wealthy young women, Olsen insists it shouldn't be of interest to anyone.

She tells America's Us magazine, "It's nobody's business if I am or I'm not (rich)."

And the star doubts she would have considered a career in showbusiness had she not started out as a youngster, insisting she is only acting now because it is all she has ever known.

She adds, "I grew up in it. It wasn't something that I aspired to. It's just something I knew. For me, I just worked. I had a job. I've had a job for 21 years."