A White House official dismissed the criticism, saying on Sunday that Mr. Shaub was simply promoting himself and had failed to do his job properly.
“Mr. Schaub’s penchant for raising concerns on matters well outside his scope with the media before ever raising them with the White House — which happens to be his actual day job — is rather telling,” Lindsay E. Walters, a White House spokeswoman, said in a statement that misspelled Mr. Shaub’s name. “The truth is, Mr. Schaub is not interested in advising the executive branch on ethics. He’s interested in grandstanding and lobbying for more expansive powers in the office he holds.”
Mr. Trump’s repeated trips to his family’s business properties — he has visited one of them on at least 54 days since moving into the White House nearly six months ago, including nearly 40 stops at a family golf course — have caused discomfort for Mr. Shaub each time.
“It creates the appearance of profiting from the presidency,” Mr. Shaub said. “Misuse of position is really the heart of the ethics program, and the internationally accepted definition of corruption is abuse of entrusted power. It undermines the government ethics program by casting doubt on the integrity of government decision making.”
Mr. Shaub recommended giving the ethics office limited power to subpoena records, as well as authority to negotiate prohibitions on presidential conflicts of interest; mandating that presidential candidates release tax returns; and revising financial disclosure rules. But he acknowledged that some of these proposals would be difficult to pass in Congress.
There are signs that lawmakers are open to considering the ideas. Representative Trey Gowdy of South Carolina, the new Republican chairman of the House Oversight and Government Reform Committee, said he was preparing to meet with Mr. Shaub. The effort could be a test of what kind of appetite Mr. Gowdy has to challenge the Trump administration as the chairman of what is traditionally the most active oversight committee in Congress.
Representative Elijah E. Cummings of Maryland, the committee’s top-ranking Democrat, also wants to discuss the ethics office and ways to strengthen it.
“I look forward to having a productive conversation with Mr. Shaub and Elijah Cummings before the outgoing director leaves office,” Mr. Gowdy said in a statement in response to questions from The New York Times about possible changes in the authority granted to the office, known as O.G.E. “The discussion will include ways to improve the ethics process and instill confidence in O.G.E.”
Mr. Cummings is already drafting legislation with the hope of gaining Mr. Gowdy’s support, members of his staff said. It will incorporate some of Mr. Shaub’s proposals, albeit the less contentious provisions that stand a chance of passing in a Republican-controlled Congress.
“The Office of Government Ethics has an impossible job under this administration because President Trump has ignored its advice, undermined its authority and openly flouted ethics rules,” Mr. Cummings said in a statement. “Now more than ever, it is important for Congress to act to strengthen O.G.E. and protect its independence.”
Mr. Shaub’s relationship with Mr. Trump has been tense since even before Inauguration Day. He publicly pushed Mr. Trump to do as every other president in recent decades has voluntarily done and sell his assets before taking office to avoid conflicts of interest.
Instead, Mr. Trump put his hotels, golf courses, office buildings and marketing agreements with properties in Turkey, India, the United Arab Emirates, Britain and other nations into a trust controlled by his adult sons and other Trump Organization executives. Those measures did not satisfy Mr. Shaub.
Mr. Shaub also pressed the White House to turn over copies of ethics waivers it had granted to lobbyists who had joined the administration that allowed them to ignore requirements that they not take actions that could benefit their former clients. The White House initially questioned Mr. Shaub’s authority to ask for copies of the waivers, before backing down.
Hui Chen, who served until recently as an ethics expert in the Justice Department’s Fraud Section, said Mr. Shaub’s proposals would give the office greater independence and power to police actions by top federal officials.
“Anytime when we see a company with a chief compliance officer making what we call a ‘loud withdraw,’ it is considered a red flag for a company,” she said, drawing an analogy to corporate America.
Mr. Shaub wants Congress to clarify that the agency has clear ethics oversight authority over all parts of the White House and that its director may only be removed for cause.
Other changes would increase the agency’s enforcement abilities and autonomy. Mr. Shaub said he did not believe the office should be allowed to conduct extensive investigations, but advocated granting it limited subpoena authority so it could make sure ethics questions were answered.
His suggestion that Congress create new conflict of interest standards for the president, and require presidential candidates to disclose their tax returns to the Federal Election Commission and have them posted by the Office of Government Ethics, may be more difficult to enact.
Historically, presidential candidates and officeholders have voluntarily released their tax returns and divested their holdings. Mr. Trump has not. “Other presidents have understood it is a pragmatic necessity,” Mr. Shaub said. “This president seems to think it is a perk of high office.”
Mr. Shaub, who is taking a job at a nonprofit group called the Campaign Legal Center, said he had never wanted the role of challenging the president of the United States. He said he regretted that his actions had at times been exploited by Democrats, including at least one effort to raise money off his work.
“I would not have picked this fight,” said Mr. Shaub, who became a junior lawyer in the ethics office in 2001 and was appointed by President Barack Obama in January 2013 to a five-year term as director. “But I have never been one to shy away from bullies.”
He said he realized it might take years to get even some of his proposals enacted, perhaps dragging into the next presidential term. He is even considering recommending that the new rules, if enacted, not take effect until January 2021 — the end of Mr. Trump’s first term — to make the effort less partisan.
“I don’t like the fair-weather friends who are supportive of the ethics program only as a political tool against this present administration,” Mr. Shaub said. “My goal from the start has been to advance the ethics program, not a political goal.”