Former Mexican President Vicente Fox tweeted on Thursday about President Donald Trump’s alleged remarks aimed at Haiti and Africa as they relate to immigration, calling Trump’s mouth “the foulest shithole” and challenging his authority to oversee U.S. policy and laws about who is allowed to live in the United States.

“@realDonaldTrump, your mouth is the foulest shithole in the world. 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 tweeted.

.@realDonaldTrump, your mouth is the foulest shithole in the world. 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? — Vicente Fox Quesada (@VicenteFoxQue) January 11, 2018

U.S. Immigration policy is created by Congress and signed into law by the presiding president of the United States.

Trump admitted that he used “tough language” during his immigration reform meeting with members of Congress on Thursday but hinted that reports of his “shithole countries” comment were not accurate.

“The language used by me at the DACA meeting was tough, but this was not the language used,” he wrote on Twitter on Friday morning.