Controversial former Sheriff Joe Arpaio on Wednesday called former President Barack Obama's birth certificate a "phony document" in an interview on CNN.

Arpaio announced Tuesday that he is running for the Arizona US Senate seat currently occupied by Sen. Jeff Flake, who is retiring from Congress at the end of his term.

Arpaio was a staunch supporter of President Donald Trump during the campaign, and was pardoned by the President in August. The former Maricopa County sheriff was convicted for defying a court order to stop racially profiling Latinos, and he has been widely criticized for his hard-line stances on immigration.

Arpaio has touted "birtherism" in the past, and, when speaking to CNN's Chris Cuomo on Wednesday evening, said he has proof that Obama's birth certificate is fake.

"We have the evidence, nobody will talk about it, nobody will look at it, and anytime you want to come down or anybody we'll be glad to show you the evidence," Arpaio said.

Cuomo then pressed Arpaio again on the topic: "So you believe that President Obama's birth certificate is a phony?"

"No doubt about it," Arpaio said.

Trump also has a history of promoting birtherism, but during the 2016 presidential campaign he denounced his past claims and said he thought Obama was in fact born in the US.

Obama was born in Hawaii.