'Material girl' Hillary Duff slammed her pop rivals, Britney Spears and Jessica Simpson for being too focused on their sexy image and neglecting their music.

Duff, 17, thinks the two pop stars are immature as they are taking off their clothes without thinking of the consequences.

Hilary said: "It's so funny, because with Jessica Simpson... a lot of people talked bad about Britney Spears and gave her so much flak, and I don't see any difference.

"I think if you feel comfortable with what you're doing, more power to you, that's what you should be doing.

"But I definitely do not think taking your clothes off or going out and getting wasted every night is a sign of maturity."

She added: "I do not want to look back years from now and go, 'Ugh, that's so embarrassing.'"