Paris Hilton and Britney Spears have been named the world's worst-dressed women in an annual US list of celebrity fashion disasters.
The pair were described as "two peas in an overexposed pod"
Fashion critic Mr Blackwell put the "style-free and fashion deprived" showbiz friends top of his list, which he has published every year since 1960.
The pair, who have often been pictured out on the town together, were "two peas in an overexposed pod", he added.
Meanwhile, Hilton has pleaded not guilty to drink driving in Los Angeles.
The heiress was arrested in Hollywood in September. She did not appear in court on Tuesday but her lawyer entered the not guilty plea.
Next on the Blackwell list was Camilla Parker Bowles, the Duchess of Cornwall, who was described as "the Duchess of Dowdy".
Actress Lindsay Lohan had gone from "adorable to deplorable", he said, while Christina Aguilera was "all crass and no class".
Mariah Carey was "Mariah the fashion pariah", American Idol judge Paula Abdul was "a fallen fashion idol" and Sharon Stone was "an over-the-hill Cruella DeVille", he declared.
But the former designer had kind words for Kate Winslet, Dame Helen Mirren, Angelina Jolie, Beyonce and Katie Holmes.