The U.S. special envoy to Haiti has resigned in protest over his nation's “inhumane treatment of migrants,” a move that represents the sharpest internal criticism yet of the Biden administration's handling of Haitian migrants.

In a resignation letter, Daniel Foote, a former ambassador to Zambia, said he could not be associated with “inhumane, counterproductive decision to deport thousands of Haitian refugees.

Foote further criticized U.S. policy toward Haiti and said the Biden administration has ignored his advice.

“Our policy approach to Haiti remains deeply flawed, and my recommendations have been ignored and dismissed, when not edited to project a narrative different from my own,” Foote wrote in the letter obtained by The Hill and first reported by PBS News.

A State Department spokesperson acknowledged Foote's resignation in a statement to The Hill, saying, "We thank Ambassador Foote for his service in this role."

"The United States remains committed to supporting safe, orderly, and humane migration throughout our region, and we engage with partners throughout the migratory corridor to impress upon them our shared responsibility for humane migration management, which includes enforcing migration laws and protecting vulnerable populations," the spokesperson said.

The Hill has reached out to the White House for comment.

Foote's resignation comes as the Biden administration faces intense backlash for its handling of Haitian migrants at the U.S.-Mexico border in Del Rio, Texas.

Thousands of Haitians are seeking to enter the country, and images this week of border agents on horseback corralling migrants stoked outrage.

Democrats have also been criticizing the resumption of flights deporting Haitians back to the island nation, which recently suffered a serious earthquake in August a month after its president was assassinated.

The U.S. has returned more than 500 Haitians via flights that began last week.

Foote was appointed special envoy for Haiti in late July following the assassination of Haitian President Jovenel Moïse. He had previously served as deputy chief of mission in Haiti.

In his letter, Foote described a country mired in poverty and gang violence and said the people of Haiti “simply cannot support the forced infusion of thousands of returned migrants lacking food, shelter, and money without additional, avoidable human tragedy.”

“The collapsed state is unable to provide security or basic services, and more refugees will fuel further desperation and crime,” Foote wrote. "Surging migration to our borders will only grow as we add to Haiti’s unacceptable misery.”

He also criticized the U.S. for its involvement in the political fallout following the assassination, backing the de facto prime minister, and warned that such interventions have “consistently produced catastrophic results.”

“The hubris that makes us believe that we should pick the winner — again — is impressive,” Foote wrote.

State Department spokesperson Ned Price said in a statement that there have been "multiple senior-level policy conversations on Haiti, where all proposals, including those led by Special Envoy Foote, were fully considered in a rigorous and transparent policy process."

"Some of those proposals were determined to be harmful to our commitment to the promotion of democracy in Haiti and were rejected during the policy process. For him to say his proposals were ignored is simply false," Price added.

"I'm not going to parse the contents of his resignation letter, but I do want to emphasize that we have active policy debates in this administration on a number of issues."

Price said it is "unfortunate" that "instead of participating in a solutions-oriented policy process, Special Envoy Foote has both resigned and mischaracterized the circumstances of his resignation."

"He failed to take advantage of ample opportunity to raise concerns about migration during his tenure and chose to resign instead," Price added.

Rebecca Beitsch and Morgan Chalfant contributed to this story, which was updated at 11:05 a.m.