An online petition to the British parliament demanding a second UK referendum on whether to remain in the European Union received a surge of support over the weekend, nearing 1 million signatures within a day of being set up.

But a stunned EU on Friday urged Britain to leave as “soon as possible” amid fears the devastating blow to European unity could spark a chain reaction of further referendums.

German Chancellor Angela Merkel and French President Francois Hollande led calls for the European Union to reform in order to survive a traumatic divorce with Britain.

In a sign that the bloc wants to move on swiftly, EU chiefs told Britain in a strongly-worded joint statement to “give effect to this decision of the British people as soon as possible, however painful that process may be.”

The uncompromising stance came after Prime Minister David Cameron said he would resign and leave the negotiations on Britain’s departure from the 28-nation club to a successor who will be named by October.

The petition was gaining tens of thousands of new signatures by the hour.

“We the undersigned call upon HM Government to implement a rule that if the remain or leave vote is less than 60% based on a turnout less than 75% there should be another referendum,” wrote creator William Oliver Healey.

Britons voted by 52 to 48 percent Thursday to abandon the bloc after 43 years of often troubled membership. Turnout on Thursday was at 72.2% of registered voters.

So many users were accessing the House of Commons website to urge a do-over of the vote that they temporarily crashed the website, though the issue appeared to have been solved by Saturday.

Parliament said it had seen “high volumes of simultaneous users on a single petition, significantly higher than on any previous occasion.”

A map of the voting indicated that most activity was in London — where most boroughs backed the “remain” camp in the referendum.

Parliament is required to respond to any petition that passes the 100,000 signature mark.

A second referendum isn’t in the cards for now, but experts say it isn’t out of the question if those who back a British exit begin suffering from buyer’s remorse.

Meanwhile over 100,000 people signed a petition for London to stay in the European Union on Friday, as Mayor Sadiq Khan said the city must have a say in Britain’s exit negotiations.

The petition on the change.org website called: “Declare London independent from the UK and apply to join the EU.”

Sixty percent of Londoners voted for Britain to stay in the union.

“London is an international city, and we want to remain at the heart of Europe,” the petition said.

“Let’s face it — the rest of the country disagrees. So rather than passive aggressively vote against each other at every election, let’s make the divorce official and move in with our friends on the continent.

“This petition is calling on Mayor Sadiq Khan to declare London independent, and apply to join the EU,” it said.

Khan himself issued a statement on the negotiations for Britain’s departure from the EU.

“It is crucial that London has a voice at the table during those renegotiations, alongside Scotland and Northern Ireland,” the pro-EU mayor said.

“Although we will be outside the EU, it is crucial that we remain part of the single market,” he said.

“Leaving the single market of 500 million people — with its free-trade benefits — would be a mistake. I will be pushing the government to ensure this is the cornerstone of the negotiations with the EU,” he said.

• Times of Israel