The woman who started the Revoke Article 50 petition says she has had three death threats over the phone and received “torrents of abuse” on social media.
Margaret Georgiadou, 77, started the anti-Brexit petition in February, but has now been left scared after being threatened.
Her petition reached 4.4 million signatures on Saturday as “one million people” marched on central London in support of a People’s Vote.
The retired lecturer tweeted: “In the past 10 hours have had three death threats over the phone, my FB account has been hacked and had a torrent of abuse on Facebook. Am closing my FB account.
“Who wants Brexit so much that they are prepared to kill for it?”
She said she was unable to attend the People’s Vote march on Saturday as she was in Cyprus but wished attendees well.
Staggering footage shows huge crowds making their way through the capital as demonstrators taking part in the Put it to the People march made their way from Hyde Park Corner towards Parliament.
Mrs Georgiadou told the BBC: "I feel terrible, I feel angry with myself because I thought I was tougher than that. But I was scared.
"I haven't even told my husband because he is very old and he would become hysterical.
"Democracy is ruled by society for society, not the majority for the majority.
London People's Vote march: In Pictures
"I want it to prove Brexit is no longer the will of the people. It was three years ago but the government has become infamous for changing their mind - so why can't the people?
"People should ask themselves, who is it that wants Brexit? It will help Putin, it will help Trump… but will it help us? I doubt it.”
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