The Virginia governor, Glenn Youngkin, was accused of creating “a culture of toxicity” in his first months in office, after campaign aides attacked a high-school student, naming and picturing the boy, for sharing a news story about the Republican official.

On Saturday, Ethan Lynne, 17 and according to his Twitter biography a Democrat, posted an article which suggested Youngkin could be trying to stop work to highlight the history of enslaved people at the Virginia executive mansion.

In response, Youngkin’s campaign account posted a picture of Lynne with the former governor Ralph Northam, next to a picture from Northam’s medical school yearbook of two men in racist costumes: one in Blackface and one in a Ku Klux Klan costume.

“Here’s a picture of Ethan with a man that had a Blackface/KKK photo in his yearbook,” Team Youngkin tweeted.

In 2019, Northam admitted being one of the men in the photograph, an admission he later recanted.

Virginia governors cannot serve consecutive terms. Youngkin beat the Democrat Terry McAuliffe, a former governor, in a bitter 2021 election in which the Republican made teaching about race and racism in US history a key campaign issue.

Amid outrage at an attack on a minor, the Team Youngkin tweet was deleted.

Speaking to the Washington Post, Lynne said: “A governor’s campaign account has attacked a minor – to me that was a new low … it was up for over 12 hours. I received no apology, no communication, nothing.”

On Monday, Youngkin said: “On Saturday night, an unauthorized tweet came from a campaign account. I regret that this happened and it shouldn’t have. I have addressed it with my team. We must continue to work to bring Virginians together. There is so much more that unites us than divides us.”

Lynne said: “While he acknowledged the situation, Governor Youngkin did not apologize and did not condemn what happened over the weekend. I still hope he does, and that he will take time to recognize the culture of toxicity he has created within his first month of office.”

A Youngkin campaign spokesman, Matt Wolking, said the tweet was deleted when it was realised Lynne was a minor.

Lynne’s Twitter biography reads: “Virginian. HS Senior. Democrat.”

“It was brought to [our] attention that this Democrat party official repeatedly elevated by [state] senator Louise Lucas as a source of official Democrat party communications is actually a minor, so the tweet was removed,” Wolking said.

The article Lynne posted was from VPM, a public radio station in Richmond, the state capital. It alleged Youngkin was converting a classroom in the executive mansion, used to educate on ties between the building and slavery, into a family room.

The article also said an archeologist and historian who worked with the two previous governors had her office cleaned out.

Lynne tweeted: “NEW: The historian tasked with teaching about slavery at the Virginia Governors Mansion just resigned after finding Youngkin converted her classroom into a family room – and emptied her office.”

He added: “Shameful.”

Corrections were later posted, saying Youngkin had not converted the classroom and the historian had resigned, but did seem to have had her office cleaned out. Lynne retweeted the correction. Nonetheless, the Youngkin campaign team attacked. Lynne said he did not notice their tweet for hours.

“In school, we are taught how to spot bullying, and their tweet last night perfectly fit that description,” Lynne wrote on Sunday, also thanking people who offered support.

“It is disgusting, disturbing, and unbecoming of the commonwealth to see the governor and his office stoop this low, especially on a public platform.”