Tory MPs voiced outrage after the Chancellor handed over the cash to the International Monetary Fund.
His decision takes the UK’s total contributions to the IMF up to £40billion — or £1,538 for every family.
Speaking in Washington, Mr Osborne said: “Jobs and growth in Britain depend on stable world economy. That needs a strong IMF.”
But Tory backbenchers said British taxpayers should NOT prop up the euro.
Peter Bone fumed: “It is outrageous more taxpayers’ money is being risked. We may as well put £10billion in the nearest litter bin.”
Fellow MP Douglas Carswell said: “George Osborne has committed millions more to bailing out a currency we chose not join.”
Shadow chancellor Ed Balls called the decision a “sticking plaster response” and said EU nations should have put more cash into their own firewall.
The loan was part of £270billion pledged to the IMF by countries including Russia, China and India.
IMF chief Christine Lagarde said this indicated the “strong resolve” of the international community to find financial stability.
Anger was fuelled by reports that the US and Canada will not be giving extra.