Pop star Demi Lovato is determined to become a role model for young girls after blaming her battles with substance abuse on a lack of inspirational figures when she was a child.

The Heart Attack singer began her career in showbusiness aged seven when she appeared on children's Tv hit Barney and Friends, but she ended up battling a host of personal issues as a teenager including an eating disorder, substance abuse and self-harm.

Lovato is now sober and insists she has no intention of relapsing, and she cites the loneliness she felt as a child star as the spark for her teenage issues.

The singer is determined to set a good example for young girls to ensure they do not make the same mistakes as she did, and reveals she has big ambitions for her future which she hopes will inspire her fans.

She tells Cosmopolitan for Latinas magazine, "When I was younger, I needed someone in the spotlight to idolise, who stood for positivity and light and happiness, and wanted to change the world. And because I didn't have that, I realised I want to do that, if only for my 12-year-old little sister...

"I'm very proud of how far I've come, but I definitely want to win a Grammy one day, and I dream of winning an Oscar. I want to tour and build my fan base and make music that will last for decades."