The writer tweeted in response to the announcement of the new Marvel NOW! title, complaining about the "D-list" talent frequently assigned to his creation, reports ComicBook.com.
"Testament to Deadpool's appeal and durability is that he thrives regardless of being regulated to D-list talent," he wrote on Twitter. "Marvel A-list never touches."
The comment inspired tweets of protest from creators including artist Dave Johnson and writer Rick Remender.
Liefeld claimed that he had been complaining about Marvel's policy of only using new and unproven talent on Deadpool, rather than an attack on the new creative team of Brian Posehn, Gerry Duggan and Walking Dead co-creator Tony Moore.
"As a parent I tell my kids it costs nothing to apologise, so here goes: I apologise and am truly sorry to everyone I insulted with my D-list comments," Liefeld later wrote. "I said it and can't take it back."
"Welcome to the D-list, @GerryDuggan @thebrianposehn @tonymoore!" tweeted Marvel editor-in-chief Axel Alonso. "Howdy Doody just put your name on the list."
Alonso's tweet was the first confirmation that the 'Moore' teased for the project is Tony Moore.
"Yes!!! I've been elevated to the 'D list' of talent," wrote Johnson. "Thanks Rob. Now if I can only learn how to ink while driving a car."
Watch a video of Liefeld inking while driving below: