A California history teacher has been placed on paid leave after comparing US president-elect Donald Trump to Adolf Hitler during one of his lessons.

Holocaust scholar Frank Navarro, who has taught at Mountain View High School for 40 years, said the school’s principal and district superintendent asked him to leave on Thursday, after a parent sent an email to school officials expressing concerns about a lesson plan for Mr Navarro's world studies class which drew parallels between Mr Trump and the Nazi leader.

“This parent said that I had said Donald Trump was Hitler, but I would never say that,” Mr Navarro told the San Francisco Chronicle on Saturday. “That’s sloppy historical thinking.”

Mr Navarro said that he believes that it was appropriate to compare the two men because he thinks it is "historically factual". Both the president-elect and Hitler, during their rise to power, vowed to deport foreigners and make their country “great again”, he noted.

“This feels like we’re trying to squash free speech,” the history teacher told the Monterey Herald. “Everything I talk about is factually based. They can go and check it out. It’s not propaganda or bias if it’s based on hard facts.”