The Mayor of London read out some of the racist online abuse he receives as he demanded action from social media firms to tackle hate speech.
Sadiq Khan suggested the level of abuse could deter other people from minority backgrounds from entering politics.
Mr Khan urged the likes of Facebook and Twitter to improve their response to criticism, or face further regulation.
Speaking at a conference in Texas, Mr Khan read out one message which included a death threat.
The mayor said he received one message saying: “Kill the Mayor of London and you will be rid of one Muslim terrorist.”
He said another message received on Twitter read: “Deport all Muslims and make London white again”, while a third said: “I wish Sadiq Khan would blow himself up like they all do.”
Mr Khan said: “I don’t read these out to be portrayed as a victim, or to ask for sympathy.
“But ask yourself this – what happens when young boys and girls from minority backgrounds see this kind of thing on their timelines – or experience it themselves?
“And what about young girls and women who are being driven from these platforms – reversing our long fight for gender equality?”
The messages formed part of his keynote speech at the South by Southwest (SXSW) festival in Austin, Texas.
Mr Khan also raised concerns over social media’s role in influencing elections and referendums, spreading fake news and enabling extremists to radicalise and brainwash others.
“Facebook, Twitter and other platforms are finally starting to react to the criticisms and are developing technology to make sure the reporting process becomes quicker and more effective,” he said.
“But with the skills and resources these companies have at their disposal, I believe it’s possible to go further and faster.”
‘Dereliction of duty’
If this does not happen, Mr Khan said more countries “will start to follow or go further than what Germany has done”.
Germany has recently introduced tough new laws so that social media companies face large fines if they fail to quickly remove things like hate speech.
Mr Khan accused politicians and governments of “sitting on their hands while the tech revolution has happened around them”.
“There’s been a dereliction of duty on the part of politicians and policymakers to ensure that the rapid growth in technology is utilised and steered in a direction that benefits us all.”