David Cameron is to meet key advisers tomorrow to assess the likely impact on Britain of the Greek referendum vote.
As ballots closed, a series of opinion polls conducted for Greek television companies all pointed to a narrow "no" vote to reject the latest austerity package offered by the country's international creditors.
If confirmed in the final count, the result would represent a remarkable victory for the country's radical left prime minister Alexis Tsipras who argued that it would strengthen his hand in demanding a better deal from the eurozone and the IMF.
But with the Greek banks running perilously short of funds, opponents have warned that it could trigger a catastrophic financial collapse that could see the country forced out of the euro and possibly the European Union altogether.
Earlier, George Osborne warned that Britain could not be "immune" from the fall-out from the vote which could have unpredictable consequences for the entire continent.
The Chancellor will meet Mr Cameron, Bank of the Governor Mark Carney, and other senior officials tomorrow morning to take stock of the situation and consider whether any further action is required by the UK authorities.
"Whatever Greece decides, Britain is prepared. We have the plans in place for whatever the outcome is," Mr Osborne told BBC1's The Andrew Marr Show.
"I don't think anyone should be in any doubt - the Greek situation has an impact on the European economy which has an impact on us. We cannot be immune from these developments.
"That's all the more reason why we have to keep our house in order, run that Budget surplus, pay down our debts, be better prepared for whatever the world throws at us.
Mr Osborne said that while there was "a lot of sympathy" in the UK for the plight of the Greek people, the country had to accept the rules of the eurozone if it wished to remain a member.
"Of course we want Greece to prosper and succeed - it's a country we feel a lot of affection for. But ultimately if you are in the single currency, there are rules you have to follow," he said.