Shadow Home Secretary Yvette Cooper has written to Twitter UK criticising its response to "appalling and unacceptable" comments made about a feminist campaigner on the site.
Addressing the threats made against Caroline Criado Perez, she said: "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."
Cooper added: "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".
More top news
Fresher and cooler as we head into the second half of the weekend.
Leah Washington, 17, had to have her left leg amputated after being trapped for hours on The Smiler rollercoaster at the theme park.
The video, obtained by ITV News, shows scores of migrants desperately trying to board lorries in a restricted area within the tunnel.