Yolanda Hadid didn't allow her children to start modelling before they were 18 because she feared they would be judged.

Yolanda and Bella Hadid

Yolanda and Bella Hadid

The 53-year-old American television personality "never" let her daughters Gig, 21, and Bella, 20, start their career in the fashion industry until they had hit the milestone because she wanted them to be "authentic human beings" who would not be insulted by any criticism they received.

Speaking about her rules, the blonde beauty - who also has 17-year-old son Anwar - told Elle.com: "I never let them work [as models] before they were 18. I didn't want anybody judging them on what they looked like. I wanted them to feel and be the authentic human beings that they are, and I think that created a lot of strength for them."

And the 'The Real Housewives of Beverly Hills' star tried to keep her brood grounded by telling them there are women who are "more beautiful" than them and they would have to be kind and act as "role models" if they wanted to stand out from the crowd, although she has praised them for their "extraordinary character".

She explained: "I always said to them, listen, there are thousands of girls that are much more beautiful than you girls, but you have an extraordinary character, and you're going to have to set yourself apart by being a role model, by showing up on time and being kind to everybody ... to the light people, the make-up, the cleaner in the back of the studio. Those are the people that you have to connect with, and that's how you can make a difference in the world."

Yolanda - who signed to Ford Models when she was younger and enjoyed a modelling career spanning 15 years - believes the industry has "completely changed" since she started working, and thinks if catwalk icons today are not role models they "shouldn't be in the business".

She explained: "When I was modelling we had no voice. We were just a pretty face. In today's world, that has completely changed. You have a platform. It's your responsibility to live a conscientious life, and to be a role model, and if you can't be that, then you shouldn't be in the business."