US army officials issued a strongly worded rebuke of Donald Trump’s campaign on Thursday as they confirmed a worker at Arlington national cemetery was “abruptly pushed aside” during an altercation with members of the former president’s staff.

The statement was the strongest official criticism yet of Trump’s controversial visit in which he gave a thumbs-up over graves as a photo opportunity and there was an alleged physical assault by two of his staffers on the army official. It came as outrage continued to mount from veterans and families of some of the service members buried there.

Adding to pressure on the election campaign of the Republican presidential nominee was the army’s revelation that Trump’s team was explicitly told in advance by a defense department official that taking photographs and video footage at the cemetery breached federal law.

The campaign ignored the warning and filmed anyway, sparking a confrontation, during the visit on Monday that one Democrat called “abhorrent and shameful”. And on Thursday the Trump campaign continued to aggressively insult the unnamed cemetery staff member caught up in the altercation, who was shoved when trying to enforce rules, after learning she had declined to press charges for fear of retribution from Trump’s supporters.

“Participants in the August 26th ceremony and the subsequent Section 60 visit were made aware of federal laws, Army regulations and [defense department] policies, which clearly prohibit political activities on cemetery grounds. An ANC employee who attempted to ensure adherence to these rules was abruptly pushed aside,” the army statement said.

“This incident was unfortunate, and it is also unfortunate that the ANC employee and her professionalism has been unfairly attacked. ANC is a national shrine to the honored dead of the Armed Forces, and its dedicated staff will continue to ensure public ceremonies are conducted with the dignity and respect the nation’s fallen deserve.”

Steven Cheung, the former president’s communication director, said the employee was experiencing something he termed “Trump derangement syndrome”. A day earlier he claimed the person was mentally ill, while Chris LaCivita, Trump’s senior adviser, called the employee “despicable”.

The ramping up of rhetoric by the Trump campaign was widely seen as an effort to deflect from growing condemnation of the candidate’s efforts to seize political capital by staging a photo opportunity at the Virginia cemetery on the third anniversary of a suicide bomb attack outside Kabul airport in Afghanistan that killed 13 US servicemen and women.

According to reports, the Arlington employee was “pushed and verbally abused” by two Trump campaign staffers after trying to prevent them entering the cemetery’s heavily restricted section 60, where recent US casualties, mostly from Iraq and Afghanistan, are buried.

Federal law “prohibits political campaign or election-related activities” within military cemeteries, Arlington officials said in a statement, noting that a report of the incident was filed with military authorities.

But Trump, who has blamed Joe Biden as well as Kamala Harris, his opponent in November’s election, for the US military’s chaotic 2021 withdrawal from Afghanistan, posted to social media on Wednesday footage of himself laying a wreath and talking with the family of one of the deceased veterans at his grave.

At a Michigan campaign event on Thursday, Trump defended his visit and accused the media of creating a scandal.

Trump said that he was invited to Arlington by the family of some of the 13 US servicemen and women killed in a suicide bomb attack ahead of the US withdrawal from Afghanistan.

“I spent a lot of time there. And while I was there, those families that asked me to be there … they said, ’Could you take pictures over the grave of my son, my sister, my brother? Would you take pictures with us, sir?’” Trump said. “I did. And then I said, farewell. I said, goodbye, and last night I read that I was using the site to politic, that I used it to politic. This all comes out of Washington.”

“They ask me to have a picture. And they say, I was campaigning. The one thing I get is plenty of publicity. I don’t need that. I don’t need the publicity.”

The fallout from the episode was gathering pace on Thursday after the family of a fallen special forces Green Beret soldier reportedly said footage of his adjacent grave was taken without their permission, and politicians and other military families stepped up to offer condemnation.

“According to our conversation with Arlington national cemetery, the Trump campaign staffers did not adhere to the rules that were set in place for this visit to Staff Sergeant [Darin] Hoover’s gravesite in Section 60, which lays directly next to my brother’s grave,” Michele Marckesano, sister of Master Sgt Andrew Marckesano, who died in 2020, told the New York Times.

“We hope that those visiting this sacred site understand that these were real people who sacrificed for our freedom and that they are honored and respected accordingly.”

Khizr Khan, father of the 27-year-old army captain Humayun Khan, who was killed in Iraq in 2004 and is buried in section 60, questioned why Trump made the visit.

Khan, who has previously criticized the former president for calling deceased veterans “suckers” and “losers”, told the Daily Beast: “He has proven his disrespect. Somebody needs to ask him, ‘You have shown that contempt multiple times and yet again, you go there.’”

Gerry Connolly, a Virginia Democratic congressman, said: “It’s sad but all too expected that Donald Trump would desecrate this hallowed ground and put campaign politics ahead of honoring our heroes.

“His behavior and that of his campaign is abhorrent and shameful. I urge Arlington cemetery to publicly release all that transpired so the American people can ensure the ground in which our nation’s heroes are buried is not being debased by a man who has no concept of service and sacrifice,” he added in a statement.

Cheung said on Wednesday that the campaign had footage of the Arlington altercation that it was willing to release, but by Thursday morning it had not done so.

JD Vance, the Ohio senator and Republican vice-presidential candidate, attempted to defend his running mate on Wednesday during a campaign stop in Erie, Pennsylvania.

Harris, he said during a speech critical of Biden and the vice-president’s handling of the Afghanistan withdrawal, “can go to hell”, insisting falsely that Trump had not “filmed a TV commercial at a grave site”.

• Michael Sainato and the Associated Press contributed reporting