The former president of Mexico has said that Donald Trump is a "false prophet" with the same "genes" as Adolf Hitler.
Vicente Fox also said he fears the Republican candidate for the US Presidential election will "run wild" if he enters the White House, and suggested Trump's election would "have grave consequences."
Fox made the comments on Friday in the Spanish city of Santander, where he was participating in the Global Youth Leadership Forum, according to Europa Press.
Describing Trump as "authoritarian" and "populist", Fox said the tycoon's appeal in the United States was based on his "old-fashioned promise" to solve all the people's problems - and likened him to an old Latin American dictator.
"They will learn", said Fox, who described Trump's promises as "a true deception," and said he was surprised that America had slipped back into an "old-fashioned imperial mentality."
If Trump becomes president, Fox suggested, Trump will go wild just like Hugo Chavez, who, he said, started out as a "common and everyday" person but showed his "other side" when he gained power.
Fox, who was president of Mexico between 2000 and 2006, has made a string of comments about Trump, which have angered the American billionaire. Earlier this week he called Trump "gringo feo" or "an ugly Yankee." Trump's camp has, in turn, rebuked Fox for his foul language.
The comments come just hours after Trump's son alluded to the Nazi party in a remark which was widely criticised.
Donald Trump Jr said that, if the Republican party was adopting the sort of electoral tactics employed by Hillary Clinton's campaign team, "they'd be warming up the gas chamber right now."
Trump has also angered Mexicans with his repeated claims that a wall will be constructed between the two countries, at Mexico's expense.