Police have arrested a man over a barrage of hostile tweets to a female journalist, including threats to rape and kill her.
The man was arrested in Manchester and is due to be questioned over threats made on the social networking site to Caroline Criado Perez after she successfully campaigned for a woman's picture to be put on a new bank note.
Scotland Yard said a 21-year-old was arrested on Sunday on suspicion of harassment offences after officers in North London, received a complaint of malicious communications on Thursday.
Twitter has faced calls to take faster and stronger action against online abuse in the wake of the incident.
Shadow home secretary Yvette Cooper has condemned the site’s response to the threats as “weak” and has written to the general manager of Twitter UK, Tony Wang, calling on him to take further action.
She wrote: ”Despite the scale and seriousness of these threats, the official response from Twitter continues to be extremely weak - simply directing Caroline away from Twitter towards the police, and, belatedly, directing users to abuse reporting forms on Twitter.
"Of course it is right to report such abuse to the police, and it is very important that they investigate and pursue this case.
"But social media platforms also have a responsibility for the platform they give users. And in particular they have a responsibility not to tolerate this kind of abuse, rape threats and potentially criminal behaviour.
"The response by Twitter has clearly been inadequate and fails not only Caroline, but many more women and girls who have faced similar abuse on your social network.
"More than 20,000 people have already signed an online petition asking Twitter to allow users to report abuse directly with one click.
"I urge you to go further and ensure that Twitter carries out a full review of all its policies on abusive behaviour, threats and crimes, including more help for Twitter users who experience abuse, a clear complaints process and clear action from Twitter to tackle this kind of persecution."
Wang had previously said that the company takes online abuse seriously.
He tweeted: "We encourage users to report an account for violation of the Twitter rules by using one of our report forms. Also, we're testing ways to simplify reporting, e.g. within a Tweet by using the ‘Report Tweet’ button in our iPhone app and on mobile web.
"We will suspend accounts that, once reported to us, are found to be in breach of our rules."
A campaign in support of Criado Perez, calling on Twitter to introduce a button to allow speedy reporting of abuse, has already received more than 12,500 signatures and she has received support from MPs and celebrities.
There are also attempts being made to organise a boycott of the free social media platform on 4 August.
Criado Perez said: "It's sadly not unusual to get this kind of abuse but I've never seen it get as intense or aggressive as this.
"It's infuriating that the price you pay for standing up for women is 24 hours of rape threats. We are showing that by standing together we can make a real difference.
"We made the Bank of England change its mind, we can do the same with Twitter."
Criado Perez, a freelance journalist, organised a campaign which included a petition signed by more than 35,500 people after the Bank of England decided to replace Elizabeth Fry with Winston Churchill on new £5 notes.
The move would have meant there were no women apart from the Queen on sterling banknotes.
Her campaign was a success, with an announcement by the Bank last week that the author Jane Austen will feature on the new £10 when it is introduced in 2017.