The model head, topped with straggly hair, appears for just a second in an episode of the fiction series that aired last year. It went unnoticed until a Reddit user flagged it, bringing swift condemnation, reported New York Daily News.
Craig Eaton, chairman of the Brooklyn Republican Party, called the grisly cameo "disgraceful" and said he would feel the same way if it was President Barack Obama's head.
"No matter what political persuasion, to put a former president in the light they did with his head on a stick is shameful," said Eaton, calling Americans to boycott the show.
Show bosses David Benioff and D B Weiss acknowledged the likeness during the commentary feature on the show's DVD boxed set, noting the decision to use the model was motivated by budget and not by politics.
"George Bush's head appears in a couple of beheading scenes. It's not a choice, it's not a political statement. We just had to use whatever head we had around," they said in the commentary.
HBO and the show's creators issued a pair of statements late Wednesday apologizing for the incident.
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"We use a lot of prosthetic body parts on the show: heads, arms, etc. We can't afford to have these all made from scratch, especially in scenes where we need a lot of them, so we rent them in bulk. After the scene was already shot, someone pointed out that one of the heads looked like George W Bush," Benioff and Weiss said.
"In the DVD commentary, we mentioned this, though we should not have. We meant no disrespect to the former President and apologize if anything we said or did suggested otherwise."
Added HBO, "We were deeply dismayed to see this and find it unacceptable, disrespectful and in very bad taste. We made this clear to the executive producers of the series who apologized immediately for this inadvertent careless mistake. We are sorry this happened and will have it removed from any future DVD production."