The Pentagon and National Guard paid professional sports teams to publicly honor soldiers at sporting events, according to a Senate oversight report released Wednesday that labeled the practice “inappropriate and frivolous.”

Since the end of 2011, the military has spent $6.8 million on sports marketing contracts, according to the report, released by Sens. John McCain and Jeff Flake, both Republicans from Arizona.

“By paying for such heartwarming displays like recognition of wounded warriors, surprise homecomings and on-field enlistment ceremonies, these displays lost their luster,” the report said. It is unclear how much of the money went to paid tributes.

In recent years, on-field flag rollouts and other ceremonies saluting military personnel have become commonplace at National Football League, Major League Baseball, National Basketball Association, National Hockey League and Major League Soccer games around the country. The majority of the contracts analyzed in the report ”” 72 of 122 ”” showed that the Department of Defense paid for the tributes that included national anthem performances, ceremonial first pitches, puck drops, color guard presentations and enlistment ceremonies.

Most of the contracts, the investigation found, included VIP suites and game tickets most likely to be given to participating troops or recruiters working at events.

The practices outlined in the report are sometimes called “paid-for patriotism” by critics. They have, the senators said, crossed the line between heartfelt gestures of goodwill and paid advertisements.

“We’re all enthusiastic to receive our men and women who are serving in uniform honored at various sporting events,” McCain said. “We are very grateful for that. Unfortunately, thanks to an in-depth investigation, a lot of that patriotism was paid for.”

More than a third of the contracts highlighted in the report were not included in a list provided by the Pentagon, the senators said. Two-thirds of the contracts found in their own investigation or reported by the Department of Defense, they said, contained some form of “paid patriotism.”

The 150-page report said that the Pentagon has not fully accounted for the “nature and extent” of the practice.

“It’s like pulling teeth,” Flake said of the Pentagon’s cooperation.

In a July letter in response to the investigation, Brad Carson, then acting undersecretary of Defense for personnel and readiness, said a review of all sports marketing and advertising contracts would be conducted by the Pentagon and National Guard.

“The issues raised in your letter are concerning,” Carson wrote to Flake.

The Department of Defense also has defended the practice in the past, arguing that the tributes are a valuable recruitment tool.

In one instance mentioned, the Air Force paid the LA Galaxy to recognize five high-ranking officers during a 2012 game. In another case cited, the National Guard paid the Seattle Seahawks to allow 10 soldiers to reenlist during an on-field ceremony before a 2014 game. The Wisconsin Army National Guard, it said, paid $49,000 to sponsor in part each Sunday performance of “God Bless America” at Milwaukee Brewers games.

Flake said he did not believe team owners and managers were aware of the practices that were ostensibly done in cooperation with their marketing personnel.

In a Nov. 2 letter, NFL Commissioner Roger Goodell informed the senators that an audit of all contracts between NFL teams and the military was being conducted to investigate recruitment funds. Any inappropriate payments, he wrote, would be refunded.

“We strongly oppose the use of recruitment funds for anything other than their proper purpose,” Goodell wrote.

This year, the senators led an effort to amend a major defense spending bill to prohibit spending taxpayer dollars on the practice and called on teams to donate profits to armed forces, veterans and their families. The senators said they are hopeful President Obama will sign it.

The money spent on the ceremonies was revealed in a May report by NJ.com, which found that over three years, the Pentagon paid 14 NFL teams for military tributes and other advertising at games, while the National Guard paid 11 teams. The New York Jets, it reported, received nearly $377,000.