(CNN) Businesses owned or branded by President Donald Trump have charged the federal government at least $1.2 million in taxpayer money for various services since 2016, records show.

Hotels, clubs and restaurants owned by Trump or bearing his name have billed various federal agencies and personnel more than $1 million since he became the Republican nominee for president, according to documents obtained by CNN and two nonprofit, government-watchdog organizations, Property of the People and Public Citizen.

The documents, mostly obtained through public records requests, do not offer a complete picture of the US government's total spending at Trump properties, but do shed light on the unique arrangement in which the same agencies Trump presides over as president have repeatedly paid his private businesses for lodging and other services. The documents -- which include invoices from Trump properties, government spreadsheets of expenses and other receipts -- also illustrate how federally funded security and staff precede and follow the President on his travels to his for-profit properties.

The Trump Organization didn't dispute the charges identified by CNN. Instead, Eric Trump, the Trump Organization's executive vice president, characterized them as bargain for the government.

"We provide the rooms at cost and could make far more money renting them to members or guests," Eric Trump said in a statement. "To infer that we are profiting is not only inaccurate but an outright lie," he added.

Trump spent at least 110 days in 2017 at properties that either bear his surname or that his family companies own, according to CNN's count. And by March 2018, Trump had spent 100 days at golf clubs bearing his name.

About half of the documented expenses involve the U.S. Secret Service, which has been charged more than $600,000 by various Trump properties between September 2016 and August 2019, though it's unclear if the Secret Service has released all records of Trump-related expenses during that time. Those charges include expenses at Trump's Mar-a-Lago Club and his club in Bedminster, New Jersey.

The Trump International Hotel in Washington, D.C., charged the Secret Service about $215,000 between 2016 and 2018, according to a list of transactions that the agency released in a response to a records request. NBC News first reported those transactions.

Trump has frequented his DC hotel on many occasions since taking office, making the steakhouse inside the hotel his preferred restaurant to dine at when he's in Washington. He's also headlined fundraisers and attended a wedding in the building.

A Secret Service spokesperson said, "Due to the nature of the agency's protective mission, the operational needs of the Secret Service can differ from those traveling on official business for other areas of government. In the daily execution of our protective mission, the Secret Service balances operational security with judicious allocation of resources."

Records also show Trump-branded properties have billed the Department of Defense about $500,000 since 2017. Those expenses involve lodging, food and other services at Trump-owned businesses or others that have paid licensing fees to use Trump's name, such as one in Panama City. The owners of the Panama hotel have since removed Trump's name from the property.

That amount also includes about $184,000 spent since August 2017 at the Trump Turnberry resort in Scotland, which is about 20 miles from an airport used by the Air Force, according to documents previously shared by Democrats on the House Oversight Committee. An Air Force review of overnight stays by air crews during refueling stops at the airport found military personnel stayed at Trump Turnberry "approximately 6%" of the time between 2015 and 2019, which would have included the Obama administration.

DOD spokesperson Jessica R. Maxwell said the department books lodging based on availability, per diem rates and suitability to meet mission requirements.

"If the Department were to cease using an available, mission ready, and publicly accessible hotel chain, which is priced within established per diem rates, based solely on politics -- then that would be a violation of our commitment to remain apolitical," Maxwell said.

Some of the government spending at Trump-branded properties overlaps with instances when Trump's children visited those properties. For example, a document released by the State Department shows about $15,000 charged at the Trump International Hotel & Tower Vancouver for a stay in late February 2017, when the President's sons, Eric Trump and Donald Trump Jr., their spouses, and the President's daughter, Tiffany Trump, attended its opening.

What government watchdogs say

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While all modern US presidents have traveled with White House staffers, military aides and Secret Service personnel, some government ethicists and advocacy groups have argued that the scale of the federal expenses at Trump-branded properties coupled with Trump's refusal to sell his ownership stake in his businesses as he serves as President breaches ethical norms.

"Americans elect a president to serve the people, not profit off them. Yet President Trump exploits his office to line his pockets with taxpayer dollars. And the amounts we're seeing are just the tip of the iceberg," said Ryan Shapiro, the executive director for Property of the People , a nonprofit organization that advocates for greater government transparency and obtained several government spending records.

Trump has refuted the notion that he has profited off the presidency.

"They say Trump is getting rich off our nation. I lose billions being President, I don't care. It's nice to be rich, I guess. But I lose billions," Trump said at a campaign rally in October.

The White House did not respond to CNN's questions about the charges.

In October, Eric Trump said in an interview with Yahoo Finance that the government has actually saved money by utilizing Trump properties.

"Any time the government comes, and if my father travels, they stay at our properties for free, meaning cost for housekeeping effectively, because you actually have to legally charge government something," he said. "We charge them like 50 bucks."

But the Washington Post reported in February that the Secret Service was billed room rates as high as $650 a night when Trump traveled to Mar-a-Lago in 2017.

Other documents suggest Trump's businesses have charged government agencies more than the cost of housekeeping. For example, a March 2017 receipt from the Coast Guard for a stay at Mar-a-Lago shows a $1,092 bill for a two-night stay. That document states the government was charged the so-called "rack rate" -- an industry term that usually implies the non-discounted price for a hotel room.

Kathleen Clark, a government ethics expert at Washington University in St. Louis, said Trump's refusal to separate from his family business while serving as president has created multiple conflicts of interest. She said at the very least Trump should reduce his travel to his properties and encourage officials not to direct funds to his businesses.

"If he had divested, we wouldn't be in this predicament, but even without divesting, he could put the public first and ensure that government officials minimize their spending at his properties... but he hasn't done that," Clark said.

Total government charges could be higher

Trump isn't the first White House official to have owned properties the government paid to use. The Secret Service paid about $170,000 to rent former Vice President Joe Biden's property in Delaware, between 2011 and 2017, according to contracting data. A Biden campaign official said the Secret Service paid the same rate as a prior tenant, who paid a price set by a real-estate agent based on market rates.

The total amount of taxpayer dollars spent at Trump properties could be much higher than $1.2 million.

While the White House has not directly disclosed payments to Trump properties, records released by the State Department suggest the White House has also purchased services from Trump properties.

In April 2017, a State Department official wrote in an email that the White House appeared to be using a government purchase card to pay for staff lodging at Mar-a-Lago, according to documents obtained by Property of the People through a records request.

Spencer Geissinger, who once served as President George W. Bush's deputy assistant for operations, said nearly every trip then-President Bush took was preceded by advance staff who prepared for the president's arrival.

Geissinger said even for presidential trips focused on rest and relaxation, travel staff included more than a dozen people. He said staffers who traveled on such trips included a chief of staff or deputy chief of staff, personal aides, two military aides, full Secret Service detail, the White House Press Secretary, the White House doctor, a White House nurse, the White House photographer, White House television staff, Navy Mess personnel "and a few other government officials who carry out functions that are classified."

In his experience, Geissinger said more than a half dozen senior staff members could be involved in the decision making behind a president's travel.