The champagne was flowing as Ashlee Simpson celebrated her 25th birthday with a poolside gathering of friends and family.

When she wasn't sipping Cristal with sister Jessica, the birthday girl was snuggling up to husband Pete Wentz at their VIP cabana at Wet Republic Pool in Las Vegas' MGM Hotel.

Despite becoming mum to little Bronx Mogli just ten months ago, Ashlee showed off her slender figure in a strappy dungarees-style playsuit as she frollicked with her hubby.

And whilst Jess was a little more subdued than her younger sister, the recently single and dogless star still seemed in good spirits, even giving Ashlee a sisterly spanking as she was presented with her birthday cake.