European leaders told Britain on Tuesday to act quickly to resolve the political and economic confusion unleashed by its vote to leave the European Union last week, after the IMF said the uncertainty could put pressure on global economic growth.
Sterling and world stock markets recovered slightly on Tuesday but investor confidence remains fragile despite policymakers saying they will take all necessary measures to protect their economies.
Last week's referendum wiped a record $3 trillion off the value of global shares and sterling fell to its lowest level in 31 years against the U.S. dollar.
British Finance Minister George Osborne, whose attempt to calm markets on Monday went unheard, said on Tuesday the government would have to cut spending and raise taxes to stabilize the economy after credit rating agency Fitch became the third agency to downgrade UK debt.
Businesses have announced hiring freezes and possible job cuts, despite voters' hopes the economy would thrive outside the EU.
Germany's financial market regulator delivered a double blow to the City of London, saying it could not host the headquarters of a planned European stock exchange after Britain leaves the EU and could not remain a center for trading in euros.
European countries are concerned about the impact of the political and regulatory uncertainty on the economies of the other 27 other EU members while the UK government works out how and when to begin withdrawal negotiations under Article 50 of the Lisbon Treaty.
European Central Bank President Mario Draghi said on Tuesday that central banks around the world should aim to align monetary policies to mitigate "destabilizing spillovers" between economies.
Draghi had added that he agreed with private economists who predict euro zone growth will be reduced by up to 0.5 percent cumulatively over the next three years due to the "Brexit" vote.
UK WARNED EU ACCESS DEPENDS ON FOUR FREEDOMS
At a summit meeting of the leaders of the EU in Brussels on Tuesday, Cameron said he hoped the UK would maintain as tight an economic and political relationship as possible with the EU.
"Britain will be leaving the European Union but we will not be turning our back on Europe," he told a news conference after a dinner at which he said many European partners expressed regret and voiced friendship for Britain.
Cameron said he told the EU summit that, "People recognized the economic case for staying, but there was a very great concern about movement of people and that was coupled with concern about issues of sovereignty. I think we need to think about that, Europe needs to think about that."
In a veiled rebuke to UK "Leave" campaign leaders such as Boris Johnson, who is vying to succeed him, Cameron said Britons would have to understand they could not keep all the benefits of EU membership without the costs.
Driving home that message, French President Francois Hollande said continued access to the EU's prized single market was dependent on accepting the so-called four freedoms of movement of goods, capital, workers and services.
"If they don't want free movement, they won't have access to the single market," he said, adding that the City of London would no longer be able to act as a clearing house in euros.