The British cartoon, which focuses on a pig and her family and friends, uses "out of date stereotypical gender-specific wording [that] prevents young girls from becoming firefighters," according to the London Fire Brigade.
The department tweeted the accusation on Sunday in response to an episode of the show titled "The Fire Engine," in which Peppa's mother is dressed as a firefighter, but is referred to as a "fireman."
"Come on @peppapig, we’ve not been firemen for 30 years," the brigade tweeted, asking the show to join along with their "#FirefightingSexism" campaign.
London Fire also criticized "Fireman Sam," a different children's cartoon that follows its male lead character as a firefighter.
David Jones, the creator of the show who says he's an ex-firefighter, told the BBC that the show "is for children" and "wasn't meant to be advertised as a recruiting post."
"Someone doesn't join the fire service when they watch Fireman Sam," he said. "They wouldn't be the right people for the job if that was their mentality."
The fire brigade later said that the involvement of a female firefighter on the show, Penny Morris, is "completely devalued by the constant use of the outdated term fireman in the catchy theme tune, title and on all merchandise. Language matters."
The conversation stemmed from an initial tweet from the department which showcased Barbie in a firefighter's outfit, and noted that she's "smashed another glass [plastic?] ceiling by becoming Barbie the firefighter!"
Officials earlier this month tweeted that the fire brigade employed 354 female firefighters.