The possibility of Britain leaving the European Union sometime in the future worries European bankers a great deal more than the prospect that Greece might be on its way out soon.

Britain's inclusion in the EU is more important to the bloc's long-term future than whatever happens to Greece,  bankers attending a financial industry conference said, even as  last-ditch talks aimed at keeping Greece solvent and avoiding a possible exit from the euro zone rumble on in Brussels.

"To me, that (Brexit) is the bigger potential nightmare," Tim Adams, president of the Institute of International Finance (IIF), said at the organisation's European meeting in Frankfurt on Thursday.

"The UK is such an important part of the European economy and ecosystem. We have one year of uncertainty hanging over us."

British Prime Minister David Cameron has promised to renegotiate Britain's relationship with the EU and then hold a vote by the end of 2017 on whether to stay in the bloc or leave.

Cameron's efforts to start that renegotiation this week have been stymied by Greece, which must persuade its creditors to unlock billions of euros in bailout funds to avoid defaulting on a debt repayment next week.

"In a mechanical sense, Grexit would disturb the workings and the structure of the European Union more (than Brexit)," said Hans Jaeckel, economist at DZ Bank.

"But for the spirit and future perspective and meaningfulness of the European Union, Brexit is the bigger risk."

The IIF was at the heart of the last major effort to stave off bankruptcy in Greece when its officials, along with senior bankers from BNP Paribas, Deutsche Bank and other lenders, spent months renegotiating the terms of Greece's 130-billion-euro debt mountain. 

                                                                                                                                                                                                          News:The Daily Star/26-Jun-2015