Britain has urged eurozone governments to find a "sustainable solution" to the debt crisis in Greece, following the emphatic rejection by voters of an austerity package demanded by creditors in return for further bailouts.
Prime Minister David Cameron vowed that the Government would do "whatever is necessary to protect the UK's economic security", as Chancellor George Osborne acknowledged that the chances of a "happy" conclusion were "diminishing" and that Britain could not be immune to the fallout from the crisis.
Mr Cameron spoke by phone with German Chancellor Angela Merkel as she prepared to go into talks in Paris this evening with French President Francois Hollande. The pair - the eurozone's biggest players - will tomorrow go into crunch talks in Brussels with other leaders of single currency states which could determine whether Greece can remain within the euro.
Greece's future membership of the single currency has been thrown into doubt by voters' rejection in Sunday's referendum of an austerity package demanded by the country's creditors in return for further bailouts. The 61%-39% No vote has plunged the European Union into what is widely seen as the deepest crisis in its history.
The Prime Minister and Chancellor met Bank of England Governor Mark Carney in Whitehall to discuss the contingency plans the Government has put in place to protect UK businesses, banks, holidaymakers and the 40,000 expats living in Greece.
Updating MPs in a statement to the House of Commons, Mr Osborne said: "This is a critical moment in the economic crisis in Greece. No-one should be under any illusions. The situation risks going from bad to worse.
"Britain will be affected. The longer the Greek crisis lasts, the worse it gets. There is no easy way out, but even at the eleventh hour we urge the eurozone leaders and Greece to find a sustainable solution.
"Meanwhile, here in Britain, we must redouble our own efforts to put our house in order, and in the Budget in two days' time, I will set out exactly how we will do that."
Downing Street made clear that Mr Cameron believes Athens and its eurozone partners must now work together on a sustainable solution to the problems caused by Greece's failure to keep up interest payments on its international debts.
The spokeswoman declined to say whether Mr Cameron thought the solution should involve Greece leaving the single currency.
Asked whether the PM wanted the country to remain in the EU, she replied: "We supported Greece becoming a member and we support the EU at 28 (member countries)."
The Foreign Office's travel advice has been updated to reflect the outcome of Sunday's poll, warning: "Visitors to Greece should be aware of the possibility that banking services – including credit card processing and servicing of ATMs – throughout Greece could potentially become limited at short notice."
British tourists are not advised to steer clear of Greece, but recommended to make sure they take "sufficient euros in cash to cover the duration of your stay, emergencies, unforeseen circumstances and any unexpected delays" as well as to take security precautions against theft.
The advice adds: "There are currently no restrictions on taking unspent euros out of Greece at the end of your stay."