Kim Kardashian West says sister Kylie Jenner unhappy with her lips since she was 10

Kim said: "I saw how for so many years she was so insecure about it. I mean, at 10 years old, she would say to me, 'How come my lips aren't big like you guys'?' And I would see this insecurity...

"For me, I gave her advice and I still stand by that advice. I think it changed her confidence so much."

The 34-year-old beauty - who has 23-month-old daughter North with husband Kanye West - insists that despite undergoing the cosmetic procedure, Kylie has no plans to have any more surgery.

She told Access Hollywood: "I think there are limits and there are boundaries, for sure. I think that you have to know the difference. She did something that made her feel better about herself and that's kind of where you have to draw the line, and she knows that ... she doesn't have a desire to do anything else.

"I'm totally okay with that because I know that's where it stops for her."

Kim also rubbished claims Kylie is too busy partying with her pals to attend school after she received criticism on social media.

She added: "She talks about this all the time herself - she's always with her friends and having fun and people would question, 'Are you going to school?' She goes to school. She's home-schooled. She has a year left. She goes to school every single day."