European Commission President Jean-Claude Juncker warned Britain today that voting to leave the EU would be "an act of self-harm" that would endanger everything Europeans had worked together to achieve. "To turn your backs on your neighbours and retreat into isolation would go against everything that the Europe and UK stand for," Juncker said during an address to Greek business leaders in Athens, adding: "To leave would be an act of self-harm." "All too often we take for granted what we have built," Juncker said, listing peace, freedom, prosperity and a "way of life that is the envy of the entire world" among the EU's achievements. "This is the patient work of generations of women and men, and we could not have done it without the British people," he added in an impassioned appeal for Britons to remain with the 28-member bloc. "Leaving the European Union would put all this at risk. It would damage what we have achieved so far. And it would diminish what we can achieve tomorrow," Juncker declared, insisting: "Europe is stronger together." Last month, Juncker had warned that British "deserters will not be welcomed with open arms" by European partners if Britain voted to leave.