US Attorney David Weiss, who is overseeing the Hunter Biden criminal probe, says in a letter obtained by CNN that he did not ask to be named as a special counsel and was never refused authority to bring charges anywhere in the country, refuting two key allegations from IRS whistleblowers.

Weiss' comments, in a letter sent Monday to GOP Sen. Lindsey Graham of South Carolina, go against claims from IRS whistleblower Gary Shapley and one of his deputies, who said they witnessed political interference in investigation of President Joe Biden's son.

They testified to Congress that during an October 2022 meeting, Weiss said he had requested to be named as a special counsel but was denied by Justice Department leadership. But Weiss said in the new letter that he never requested special counsel status, but rather explored becoming a "special attorney" under a different statute.

"I have not requested Special Counsel designation," Weiss wrote to Graham on Monday. "Rather, I had discussions with Departmental officials regarding potential appointment under 28 U.S.C. § 515, which would have allowed me to file charges in a district outside my own without the partnership of the local U.S. Attorney."

Weiss said he got these assurances "months before the October 7, 2022, meeting referenced throughout the whistleblowers' allegations."

The prosecutor also wrote that he has "never been denied the authority to bring charges in any jurisdiction." Shapley claimed that Weiss said in that same October 2022 meeting he wasn't the deciding person on whether to indict Hunter Biden, because political appointees had blocked him from bringing charges in Los Angeles and Washington, DC.

Shapley and his deputy raised their concerns in congressional testimony that was made public last month by House Republicans. The Justice Department and Attorney General Merrick Garland have denied that there was any political interference in the Hunter Biden criminal probe, which led to a plea deal where the president's son will admit to two tax misdemeanors, resolve a felony gun charge and likely avoid jail time.

Lawyers for Shapley told CNN on Monday that the letter shows that "Weiss' story continues to change."

"As a practical matter, it makes no difference whether Weiss requested special counsel or special attorney authority. Under no circumstances should 'the process' have included the political appointees of the subject's father, because Congress and the public had been assured it would not -- but it did," they said.

In the letter, Weiss also declined to comment on the internal FBI document from 2020 that contained uncorroborated allegations that Joe Biden and his son Hunter were involved in a foreign bribery scheme. Weiss said Graham's questions about the matter "relate to an ongoing investigation."