LONDON — Hours after successfully campaigning to have a woman — Jane Austen — featured on a new British banknote, Caroline Criado-Perez was bombarded with rape and death threats. The vast majority came via Twitter.

At the peak of the frenzy last month, the 29-year-old freelance journalist was receiving about a threat every minute. Some of the politer messages said “no means yes” and “kill yourself before I do,” and were written, she said, by “men who want women to shut up.”

While online abuse is not new to these isles, the threats against Criado-Perez have emerged as the highest profile of several similar incidents, with the sheer quantity and graphic nature of the missives shocking the usually unshockable British public.

The uproar is the latest in Britain’s uneasy relationship with Twitter, a site that has become a tool for democracy in many countries but that has come under heavy fire here from government officials, sports stars and celebrities, among others.

After Criado-Perez and a Labor Party member of Parliament, Stella Creasy, reported the abuse to police, two people were arrested on suspicion of harassment. Twitter bosses, who are expected to be called in front of a British parliamentary committee in the fall to discuss online abuse, struck a conciliatory note Saturday with Tony Wang, general manager of Twitter UK, tweeting an apology to women who have been subjected to threats on Twitter.

“The abuse they’ve received is simply not acceptable. It’s not acceptable in the real world, and it’s not acceptable on Twitter,” he said.

What to do about the abuse has become a major topic of discussion here after several prominent women publicly complained about harassment, including Creasy and another member of Parliament, Claire Perry. In addition, several female journalists received an identical bomb threat via Twitter. The threat was also sent to Sara Lang, social media manager for Washington-based AARP.

The current system of reporting abuse on Twitter is “completely impractical for someone drowning under a wave of threats,” Criado-Perez said. Most of the threats against her probably came via Twitter, she said, because “it’s public yet anonymous. There’s a kind of game element involved as well . . . there’s a sense of mob mentality that encourages people to get involved.”

In response to Criado-Perez’s case, a petition on Change.org calling for Twitter to add a “report abuse” button has attracted more than 125,000 signatures.

Twitter on Saturday said it is working to install such a button on all of its platforms — one already exists on its iPhone app — and that the changes will apply worldwide.

“It comes down to this: people deserve to feel safe on Twitter,” Del Harvey, Twitter’s senior director of trust and safety, and Wang wrote in a blog post Saturday, insisting they take online abuse seriously. They said they were hiring extra staff to monitor reports of abuse and were “exploring new ways of using technology to improve everyone’s experience.”

But some have wondered whether Twitter, which has long described itself as merely a platform that enables communication, should even be in the hot seat. One Twitter user on Saturday told Wang that his apology was akin to Microsoft saying it was sorry for an unkind e-mail sent via Hotmail.

Wang responded by saying that while Twitter isn’t responsible for the abuse written by others, “platforms have rules of engagement and we are working hard on them.”

His apology came as the London Metropolitan Police said they were investigating allegations made by eight people relating to “harassment, malicious communication or bomb threats” sent via Twitter.

Faced with the daunting logistics of playing sheriff in a world where 400 million tweets are sent every day, the police have also been urging Twitter to take more responsibility over how to respond to users who violate their rules.

But advocates of free speech are nervous about the implications of Twitter cracking down on torment, however cruel.

“The worry is that the abuse button will be abused,” said Robert Sharp, a spokesman for English PEN, a literary group that promotes freedom of expression. “It puts the power of censorship into the hands of those who would be offended, which is fine when it’s a rape threat. But the same technology will be used by Christians to censor atheists, used by atheists to censor Christians, and so on.”

Although some women seem to ignore the abuse, an increasing number are shouting back by retweeting.

Mary Beard, a professor of classics at Cambridge University and a TV host, retweeted a vulgar note from a user. One of her followers saw it and offered to supply her with the postal address of the user’s mother.

The user immediately expressed regret, tweeting: “I was wrong and very rude. Hope this can be forgotten and forgiven.”