The 20-year-old soul singer has confirmed that she is keen to top her previous efforts after starting work on the follow-up disc.
"I love the songs on 19, but I don't think they're the best I can do," she told the Daily Star. "I've started writing new songs, and they've got more depth to them.
"I've grown up loads in the last year. I started as a child, but I'm almost 21 and I'm almost a fully-fledged adult."
The star also claimed that she would not be as successful if Amy Winehouse had not been discovered.
She explained: "Amy Winehouse started it all. It's good that Duffy and I are doing well, but I think it's part of the Amy thing. The world just wants more Amy."