David Cameron has promised to fight "very hard" in Brussels to ensure the British taxpayer does not shoulder any of the cost of a European bailout of Greece.
The Prime Minister said he "absolutely" did not think the UK should contribute towards a possible 12 billion euro (£10.6bn) package for the ailing eurozone country.
He would be taking that message to fellow European Union leaders when they gather in Brussels later this week, he added. Mr Cameron was speaking at a conference for chief executives organised by The Times newspaper.
Asked whether Britain could afford to help the bailout, Mr Cameron said: "I absolutely don't believe we should. I don't believe that we will and I shall be fighting very hard to achieve that at the European Council this week."
EU finance ministers are refusing to hand the Greek government a second bailout package of 12 billion euro unless it agrees to implement a 28-billion euro (£24.8bn) set of austerity measures which include tax increases and massive spending cuts.
Finance ministers meeting in Luxembourg put off until July 3 a final decision on the loan instalment, without which Athens would be forced to default on its debts.
Downing Street has said Britain has not been asked to contribute towards the latest bailout, which is expected to involve only the 17 members of the eurozone.
However Treasury Financial Secretary Mark Hoban told MPs that the burden of supporting Greece may have to be shared by the International Monetary Fund, of which the UK is a major shareholder with a total subscription of £19.7 billion.
The crisis in Greece has prompted forecasts of the European single currency's demise, with former foreign secretary Jack Straw warning that the euro "cannot last". He urged ministers to prepare Britain for "alternatives" to the European single currency.
Mr Straw told the Commons that the UK's potential exposure to Greek debt, including of private banks, totalled £8 billion. The Government needed to recognise the "mood change" in Europe, with former europhiles "contemplating the end of the euro as we know it", he said.