British pop star Pixie Lott signed up as an ambassador of a children's charity following an emotional meeting with a seriously ill young girl.

The Mama Do hitmaker spent time with cancer sufferer Bella Restuccia last year (12) through U.K. organisation Rays of Sunshine, which grants wishes for sick kids.

The singer was so moved by the four year old's courage, she agreed to become an ambassador the charity.

She says, "I am absolutely honoured to become an ambassador for Rays of Sunshine. Bella’s twinkly, smiley face made my day and I only hope I can help the charity to spread more beautiful smiles."

Lott joins fellow Brit pop acts One Direction, JLS and Leona Lewis, who are already ambassadors for Rays of Sunshine.