Saying it's all in fun to encourage fashion consciousness, Blackwell heaped venom on Beckham, his No. 1 choice on the list, which was released Tuesday.
"Forget the fashion spice, wearing a skirt would suffice! In one skinny-mini monstrosity after another, pouty Posh can really wreck-em," he said in a statement.
An e-mail message to Beckham's publicist, Cheryl Maisel, wasn't immediately answered.
Blackwell listed the Spice Girls as No. 1 in his 1998 worst-dressed list, deriding the group as "the only spices on the planet that have no taste."
Britney Spears, who has made the list many times before, is missing this year.
"I felt that it was inappropriate at this time to make comment, when her personal life is in such upheaval. I hope 2008 is a better year for her," Blackwell said.
The top 10 roll-call of fashion dishonors also includes:
No. 2: Amy Winehouse -- "Exploding beehives above, tacky polka-dots below, she's part '50s carhop horror."
No. 3: Mary-Kate Olsen -- "She resembles a tattered toothpick -- trapped in a hurricane."
No. 4: Fergie -- "Yes, when it comes to couture chaos, guess it's all in a name!"
His top 10 also includes Kelly Clarkson, Eva Green, Avril Lavigne, Jessica Simpson, Lindsay Lohan and Alison Arngrim.
He also released a Fabulous Fashion Independents list that includes Reese Witherspoon, Jemima Khan, Beyonce, Angelina Jolie, Helen Mirren, Nicole Kidman, Katie Holmes, Kate Middleton, Katherine Heigl and Cate Blanchett.