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The federal government's ethics watchdog warned President Donald Trump's transition team last fall about its “unprecedented” and risky approach to staffing the cabinet, according to new emails obtained by NBC News.

Walter Shaub, Director of the Office of Government Ethics (OGE) who has clashed with Trump's administration, wrote to the then-president-elect's top lawyer on Saturday, Nov. 19, with a warning about “imminent” cabinet appointments.

“I am not sure whether you are aware that announcing the cabinet without first coordinating with OGE is unprecedented,” he wrote, “and creates unnecessary risk for both the President-elect and the prospective nominees.”

Shaub stated that his ethics office had “not been involved in the process as to any of these individuals.”

While the ethics office had been in contact with Trump aides during the campaign, Shaub recounted how after the election, the ethics “process we put in place has broken down.”

Trump White House officials did not immediately return requests for comment.

The email, sent to Don McGhan, now White House counsel, was sent shortly after Trump's election and before he had publicly named any of his cabinet selections. Still, Shaub's letter said Trump aides ignored or rebuffed “several” requests from the ethics office to schedule a call or meeting with McGahn.

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“At present, we have no reliable lines of communication with the transition team — a circumstance that is also unprecedented,” Shaub wrote.

The emails were obtained through a Freedom of Information request from NBC News and The James Madison Project, both of whom were represented by the law office of Mark S. Zaid.

EXCLUSIVE FOIA:

Ethics Director tells Trump's lawyer the ethics communication process has "broken down" https://t.co/ZBt3ZjKBea pic.twitter.com/qEgdI4kay8 — Ari Melber (@AriMelber) February 2, 2017

The emails echo earlier transition communications, which showed Trump aides rebuffing the office’s effort to offer ethics advice on blind trusts and nominees.

READ THE EMAILS OBTAINED BY NBC NEWS HERE

The friction over nominees went public in January, when Shaub sent a letter to the senate arguing that confirmation hearings should occur only after ethics reviews were complete.

Ethics experts said Shaub is right that other transition teams and administrations worked directly with the office.

Norm Eisen, a former Obama ethics official who is suing the Trump administration alleging Constitutional violations, said past administrations have benefited from choosing “to engage early and often with OGE about nominees.”

“This email sheds light on why the Trump nominees are, as a whole, the most conflicted group that I recall,” Eisen told NBC News after reviewing the correspondence.

“That problem starts at the top,” he added, “with the president's own unresolved conflicts.”

Mark Zaid, a national security lawyer who oversaw the FOIA request, said the newly disclosed emails raise a “question of how serious this administration will take its ethical obligations, beyond what its private, paid lawyers tell them they can or cannot do.”

Trump’s aides and private counsel have previously emphasized that he is following all relevant federal laws, that many ethics laws “have historically not applied” to the president, and that he is building "the most qualified administration in history."

White House spokesman Sean Spicer has stressed Trump’s appointees have been submitting the paperwork required under law for his nominees.

And while the Trump team’s decision to forego wider input from the ethics office is unusual, it is well within their legal discretion.

As Director Shaub noted in one of his transition emails, Trump aides were “under no obligation to follow the tradition.”

But staffing a cabinet with robust ethics oversight, he added, was a “tradition evolved as a result of hard lessons.”