Acting couple Kristen Bell and Dax Shepard are calling on fans and fellow parents to bombard editors of a tabloid with complaints after ranking the best and worst celebrity moms in a recent issue.

The Frozen star and her husband Shepard have been leading a boycott of magazines which buy and print photos of celebrities and their children without parental permission as part of the No Kids Policy they launched last year (14).

Bell, who welcomed their second child in December (14), managed to convince editors at a slew of top publications to curb their use of such pictures, but some have ignored her pleas and the actress was outraged to discover that last week's (ends05Jun15) Star magazine cover featured the headline, "Best & Worst Moms!", alongside snaps of celebrity mothers and grades for their parenting skills.

Among those featured were Kim Kardashian, who was given a D- for spoiling her daughter North; Naomi Watts, who received a C+ for how she's raising her two sons with partner Liev Shreiber, and Jessica Alba, who was awarded an A for how she takes care of her two daughters.

However, the cover story and the multi-page spread inside the magazine have not sat well with Bell and Shepard, who took to their Twitter.com blogs late on Tuesday (09Jun15) to vent about the article and urge members of the public to make their disdain known.

Shepard sent out the first call to action, telling his fans, "Please let @Star_News know how you feel about their cover ranking "Best And Worst Moms." Mine are leaning towards repugnant."

Bell reposted her husband's message and added, "i hope no one responsible for this weeks (sic) cover of @Star_News is raising children of their own. shame on them...

"Hey moms- FOR REAL- lets (sic) tell @star_news how we feel about them attempting to publicly shame other moms."