The pregnant singer, who is married to Fall Out Boy rocker Pete Wentz, celebrated turning 24 with a fancy dress bash at her parents' Los Angeles home last weekend.

One guest revealed: "It had a white-trash theme. Ashlee wore Daisy Duke hot-pants and platform flip-flops with a bathing suit and a fake tattoo around her belly."

Ashlee's sister Jessica and her father Joe also got into the party spirit by dressing up in "crazy" outfits.

Another guest told People magazine: "Joe wore a cut-off muscle T-shirt and a mullet wig. It was funny. Jessica was wearing a crazy leopard-print dress that showed off a lot of cleavage."

Revellers included Christina Aguilera, Nicole Richie and her Good Charlotte rocker fiance Joel Madden.

Guests were treated to chicken fingers, French fries, corn dogs and macaroni cheese.

This isn't the first time Ashlee - who is reportedly due to give birth at the end of the month - has thrown a fancy dress birthday party.

Last year, Ashlee asked guests to don prom dresses, fingerless gloves and vintage tuxedos for her 80s prom-themed bash.

One friend said: "Ashlee loves throwing themed parties and wearing costumes."