Former Mexican president Vincente Fox called Donald Trump’s mouth the “foulest shithole in the world” in a tweet on Thursday.

Fox made the comments after Trump’s remark about American taking people from “shithole countries” went public.

“Your mouth is the foulest shithole in the world,” Fox tweeted at Trump.

“With what authority do you proclaim who’s welcome in America and who’s not. America’s greatness is built on diversity, or have you forgotten your immigrant background, Donald?”

Fox and Trump have sparred in the past over Trump’s repeated claim that Mexico would pay for a multi-billion dollar border wall on the southern border of the US.

Trump reportedly made the controversial comments while discussing immigration from Haiti, El Salvador and African countries.