But in a May 17 letter, Mick Mulvaney, director of the Office of Management and Budget, questioned whether the Office of Government Ethics has legal jurisdiction to get information about waivers that have been granted. He said the Justice Department's Office of Legal Counsel may needed to be consulted.
"I therefore request that you stay the data call until these questions are resolved," Mulvaney wrote Shaub in a letter first reported by the New York Times.
Shaub responded forcefully with a nine-page letter to Mulvaney Monday night, denying his request to back off.
"The unusual nature of your letter highlights OGE's responsibility to lead the executive branch ethics program with independence, free from political pressure," he wrote. "Accordingly, OGE declines your request to suspend its ethics inquiry."
The letter, posted on OGE's official Twitter account, was accompanied by voluminous documents attesting to the agency's authority to collect information, examples of the executive branch complying with past requests and previous calls by lawmakers for OGE to disclose such data in a public format.
Among the attachments: a memo by an OGE attorney describing a May 17 phone call with a White House lawyer described as "less collegial" than routine conversations with other ethics officials.
Former OGE officials said the agency has clear authority to seek documentation under the 1978 Ethics in Government Act. Without such reports, they said, it is impossible to know how many appointees have been granted exemptions from ethics rules — and how much leeway they have under the waivers.
"This is unprecedented interference with OGE," said Don Fox, a former general counsel and acting director of the ethics office.
"The Ethics and Government Act was part of a whole package of post-Watergate legislation that had a common theme of transparency," he added. "If there is nothing to hide, why hide it?"
OMB officials did not respond to requests for comment.
The tussle centers on OGE's effort to determine whether the administration is complying with federal ethics regulations, including an executive order Trump signed in January that, among other measures, prohibits former lobbyists who join the government from participating in any matter they lobbied on for two years.
Trump has not disclosed how many waivers have been granted to appointees who are in violation of his order, even as his administration has tapped numerous lobbyists for posts.
In contrast, the Obama administration regularly released copies of waivers that explained why it was in the public interest to hire appointees whose past lobbying work or employers put them in conflict with ethics rules.
Trump's ethics order also stripped out an Obama-era clause requiring OGE to provide an annual public report detailing who has received ethics waivers.
Shaub now appears to be seeking to compile a public record by reviewing waivers granted in the past year.
Mulvaney's pushback is the latest episode in which administration officials have questioned the reach of OGE.
Earlier this year, Stefan Passantino, the White House's designated ethics official, argued in a letter to Shaub that many ethics rules do not apply to presidential staffers.
In response, Shaub called Passantino's assertion "extraordinary " and "incorrect."