European leaders are racing to save the latest rescue plan for the eurozone after financial markets reeled on Tuesday on fears that Greece’s proposal to hold a referendum on its second bail-out package could lead to a disorderly default by Athens.

Reacting with scarcely disguised anger to Athens’ unexpected move, Angela Merkel, Germany’s chancellor, and Nicolas Sarkozy, France’s president, summoned George Papandreou, Greek prime minister, to emergency talks in Cannes on Wednesday with Christine Lagarde, managing director of the International Monetary Fund, and the heads of the leading European institutions, to buttress the eurozone’s position on the eve of the G20 summit of world economies.

In a joint communiqué, the French and German leaders said they were “determined to ensure the implementation without delay of the decisions adopted at the eurozone summit”, saying they were “more necessary than ever today”.