US Vice-President JD Vance has urged fellow Republicans to stop "whining" about a controversial attack ad that featured a Democratic candidate's estranged mother calling her a liar.

While campaigning in Ohio for Vivek Ramaswamy, the Republican candidate for governor, Vance said he was "a little bit disgusted" by criticism from members of his own party.

In the ad, Donna Arthur, the mother of Democratic candidate Amy Acton, said her daughter "lied her entire life". It does not mention that Arthur's husband was charged with raping Acton when she was a child.

The Ramaswamy campaign have claimed credit for the ad, and have paid millions to have it advertised around the state.

Acton's brother is among those who have condemned the ad, saying turning alleged sexual assault into "a political talking point" was a "despicable low".

Acton and her brother were removed from their mother's custody when her stepfather, Cledith Arthur, was arrested and charged in 1978.

That is when she last spoke to her mother, Acton said in an interview with The Vindicator, an Ohio news outlet. The Arthurs fled Ohio and Cledith Arthur was never prosecuted on the rape charge. He died in 2004.

When the ad featuring Donna Arthur was initially released to social media on Monday evening, it did not say who the video was paid for or authorised by. Ramaswamy confirmed on Tuesday that it came from his campaign, and he later pledged to spend $4m (£2.9m) to further air it.

The move has drawn a bipartisan backlash.

Former South Carolina Governor Nikki Haley, who ran against Ramaswamy for the Republican nomination for president in 2024, said "he's a bad guy. It's a shame he continues to get away with it".

Vance, when asked by BBC News if he thought the ad was appropriate, answered: "It's not really my concern."

"What is my concern is who's going to govern the next generation of American government."

He also said he was "a little bit disgusted" by members of his own party who "are whining more about that advertisement than they are about what the congressional Democrats and other Democrats want to do to the United States of America".

Vance, a former Ohio senator, later defended the ad at a rally for Ramaswamy, saying: "Now the media and the Democrats in the state of Ohio are obsessed because guess what? Vivek Ramaswamy had the audacity to run a TV commercial which calls it out like it is, and calls Amy Acton a liar."

When asked about Ramaswamy's ad on Wednesday, Trump said: "I know nothing about it. I heard the mother went very rogue on the daughter."

He added: "It's a very unusual situation to have a mother hate a daughter that much. But I dont think that has anything to do with Vivek."

Acton's team released its own campaign ad on Tuesday, a video featuring her brother, Philip Stearns, recounting childhood abuse and saying "Amy always got the worst of it".

"Shame on Vivek," he says in the 30-second clip. "It's the contempt he has for Amy. It's the contempt he has for Ohio."

Other Republicans, including ones running for statewide office, have now criticised the ad.

Ohio Senator John Husted, who is up for re-election, told the Associated Press: "I would not have run that ad."

Ohio Secretary of Frank LaRose, who is running to be state auditor, was another Republican coming out against the ad.

"I will say that, you know, candidates will answer for their own ads, that, you know, I probably wouldn't run an ad like that, but every candidate gets to make their own decision," he told WSYX-TV, external in the city of Columbus.

Political attack ads are not a new feature of US politics, but David Lublin, a professor from American University's School of Public Affairs, told the BBC that "they have become more intense, and the boundaries have stretched in terms of what one attacks about".

Lublin said it was not new for relatives to be used against a political opponent, mentioning family members who testified against Robert F Kennedy Jr before he was confirmed as health secretary.

"But this is of a different order," he said. "They're estranged not over policy but over a rape allegation."

Lublin believes President Donald Trump's rhetoric and campaigns have helped act as a catalyst for the coarsening of American political discourse – mentioning the time Trump mocked a reporter in Ohio who had a disability.

"We live in an age where certainly many candidates can appear mean and even inappropriate at times," Lublin said, adding: "The key purpose of attack ads isn't necessarily to convert the followers of your opponent, but more to depress their turnout."

He expects the Ramaswamy attack ad to backfire, saying it could be an indication that his campaign is desperate to swing momentum in his favour in the increasingly competitive race for Ohio governor – even though a Democrat has not been elected governor there in over two decades.

Cook Political Report, a nonpartisan website that rates and tracks US elections, has moved the Ohio governor's race from "leans Republican" to "toss up", meaning neither candidate has a clear advantage.