The leaders of Germany, France and Italy have insisted that no Brexit talks of any kind can begin until Britain has formally applied to leave the European Union, which EU officials expect to happen before the end of the year.

On the eve of a crunch summit in Brussels, the German chancellor, Angela Merkel, said she, president François Hollande of France and Italy’s prime minister, Matteo Renzi, had agreed at their meeting in Berlin that “there will be no formal or informal talks about Britain’s exit” until the UK has triggered article 50, the untested procedure that governs a member state leaving.

Hollande urged Britain to “not waste time” in launching the leaving process. “Being responsible means not wasting time in engaging with the question of Britain’s departure and setting this new impulse we want to lend the new European Union,” he said, adding that “nothing is worse than uncertainty – and Britain has already had painful experience of this”.

Fearful of a prolonged period of political and economic uncertainty, European leaders are eager for the UK to make a swift start on the marathon task of extricating itself from the bloc by triggering article 50 as soon as possible.



But London is reluctant to launch formal exit proceedings yet. Chancellor George Osborne said the UK would activate Article 50 only when it has a “clear view” of how its future relations with the bloc would look.

David Cameron has left the task to his successor and leading Brexit campaigners have repeatedly said they want informal talks on the possible terms of a withdrawal deal before locking Britain into the strict two-year timeframe laid down in the article 50 process.



Facebook Twitter Pinterest Boris Johnson has said there is no rush to trigger article 50. Photograph: Ben Stansall/AFP/Getty Images

Brussels has also emphatically ruled out informal talks on a possible trade deal before the UK triggers article 50. “No notification, no negotiation,” one EU official said. A diplomat added: “If they treat their referendum as a non-event, we will also treat their referendum as a non-event.”

Cameron is due to attend the Tuesday evening summit dinner and explain Britain’s position before going back to London, leaving the remaining 27 member states to discuss on Wednesday how to handle the biggest blow to the bloc in its 60-year history.



Merkel promised the 27 remaining members would push forward with the European project, saying the leaders would “suggest to our EU colleagues that we put in place a new impulse” focused on a new collective push for cooperation in areas including “interior and exterior security, the fight against terrorism … and economic growth and competitiveness”.

“It’s above all important that we have enough jobs,” she said. “We want to think above all about young people. The young people of the UK overwhelming voted for remaining in the EU and young people in our countries have justifiable expectations of the EU offering them perspectives.

She had earlier said she had “a degree of understanding” for the fact that Britain may need “a certain amount of time to analyse things”, but warned that a “long-term suspension” of the question would serve no one’s interests.



The EU has no legal means to force Britain to launch the exit process and diplomats in Brussels now believe the UK should probably be given until the end of the year at the latest to start the withdrawal process, allowing it time to leave the EU before European parliament elections and the appointment of a new European commission in 2019.



Some, however, have warned Britain “may never” trigger the formal divorce process because the tight deadline for talks puts the leaver in a weak position. “I personally believe they will never notify,” one diplomat said. “The moment you push the button you’re in a stupid negotiating position.”

At the start of three days of frantic diplomacy to contain the fallout from Britain’s historic leave vote, the US secretary of state, John Kerry, warned in Brussels that the UK’s departure would have “consequences” demanding “sensitive, thoughtful, responsible and strategic” leadership.

Kerry said after meeting the EU’s foreign policy chief, Federica Mogherini, that all concerned would need to keep their heads, and refrain from punishing Britain. It was “absolutely essential that we stay focused on how, in this transitional period, nobody loses their head, nobody goes off half-cocked, people don’t start ginning up scatterbrained or revengeful premises”, he said.

The president of the European parliament, Martin Schulz, warned this weekend that a period of limbo would “lead to even more insecurity” and said the Brussels summit was the right time to begin formal exit proceedings.



There was pressure, too, from within Merkel’s own government: the head of her Social Democrat coalition partners, Sigmar Gabriel, called for “decisive action instead of indecision”.

Finland’s prime minister, Juha Sipilä, said Britain should leave “as soon as possible”. Describing Britain an “exceptionally important partner”, he acknowledged it needed “some time to bring its own ranks into line” and that a suitable time to begin the exit process would be in the autumn.

EU officials have said it would be “unrealistic” to expect Cameron to initiate the exit process at a time when Britain was in “a very significant political crisis, not only of the leadership of the ruling party … but a crisis that goes much deeper”.



The French finance minister, Michel Sapin, said there was no difference between France and Germany on the timetable for a withdrawal. “Should Britain go quickly?” he said. “Yes. France, like Germany, thinks that Britain voted for Brexit, and Brexit should be put in place starting now.”



Günther Oettinger, Germany’s commissioner, also sounded a warning note over too long a delay: “Every day of uncertainty prevents investors from putting their funds into Britain, and also other European markets,” he said. “Cameron and his party will cause damage if they wait until October.”

Diplomats in Brussels, meanwhile, have not stinted on their criticism of Cameron’s catastrophic decision to ignore their warnings and go ahead with a referendum on Britain’s EU membership.



Cameron reportedly told the commission’s president, Jean-Claude Juncker, at a 2014 G20 summit that he could win a referendum “by a margin of 70 to 30”. Juncker replied that even Luxembourg would not vote to stay in the EU by such a big majority, according to one EU diplomat.

Brussels insiders are also frustrated and angry that Cameron did not use the UK reform deal – painstakingly agreed by all EU member states in February – to defend the EU during the campaign. “You don’t reverse a perception between 19 February and 23 June that you have created,” the diplomat said.

As shockwaves from the vote continued to spread, EU officials also said the bloc was preparing to move its European Banking Authority from London, setting up a race led by Paris and Frankfurt to host the regulator.