A petition calling for Theresa May to cancel Brexit by revoking Article 50 has passed a million signatures, Trendreports citing BBC News.
Parliament's petitions committee tweeted that the rate of signatures was "the highest the site has ever had to deal with", after the website crashed.
It comes as the prime minister is in Brussels to ask the EU for a delay to next Friday's Brexit date.
Downing Street said the prime minister "has said many times she will not countenance revoking Article 50".
The PM's spokesman added: "The PM has long been clear that failing to deliver on the referendum result would be a failure of democracy and a failure she wouldn't countenance."
Revoke Article 50 has been trending on Twitter as people were urged to sign it. At one point, the petitions committee said there were nearly 2,000 signatures a minute.
The petition's heat map shows the constituencies with the highest number of signatories, including seats in Bristol, Edinburgh, Manchester, Oxford, London, Cambridge and Brighton.
It is not the most popular ever on the Parliament website. A petition for a second EU referendum in June 2016 attracted more than four million signatures and was debated in the Commons - but thousands of signatures were removed after it was discovered to have been hijacked by automated bots.
Another popular petition aimed to prevent US President Donald Trump from making a state visit, which attracted 1.8m signatures.
People signing petitions on the Parliament website are asked to tick a box saying they are a British citizen or UK resident and to confirm their name, email address, and postcode to sign.
Data from the petitions website on Thursday afternoon suggested more than 960,000 signatures were from people who said they were from the UK, nearly 9,000 from France, nearly 5,000 from Spain and nearly 4,000 from Germany, among others.
A Commons spokesman said signature patterns are investigated to check for fraudulent activity and suspect signatures are removed, including those that are "clearly bots".
He added: "Anyone who is a UK resident or a British citizen can sign a petition. This includes British citizens living overseas."
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