European leaders have told the United Kingdom they expect Article 50, the clause under which the formal process of leaving the EU takes pace, to be triggered immediately so negotiations over the terms of the UK's exit can begin.
This puts Europe's top politicians at odds with the UK just hours after the results of the referendum became clear and David Cameron dramatically announced his resignation.
In a statement made alongside his wife, Samantha, outside Downing Street, Cameron said he would leave the decision over the timing of Britain's formal exit from to his successor, expected to be in place by October.
However, in a joint statement from the leaders of the the European Council, Donald Tusk, the European Parliament, Martin Schulz along with Mark Rutte, holder of the rotating presidency of the European Council and the President of the European Commission, Jean-Claude Juncker, the EU's top brass called on Britain to get a move on.
"This is an unprecedented situation, but we are united in our response … The Union of 27 member states will continue.
"We now expect the UK government to give effect to this decision of the British people as soon as possible, however painful that process may be. Any delay would unnecessarily prolong uncertainty.
"We stand ready to launch negotiations swiftly with the UK regarding the terms and conditions of its withdrawal from the EU."
Boris Johnson, the favourite to succeed David Cameron once he steps down, also indicated he was in no rush to begin formal negotiations, while Nicola Sturgeon signalled her intent to hold a second referendum on Scottish independence before the UK actually leaves.
The statement from the EU leaders added: "There will be no renegotiation" with the UK, but said it hopes the UK remains a "close partner".