French President Emmanuel Macron said on Thursday that growing divisions among member states and the absence of a "joint project" posed the biggest risk to the European project.
During an interview with German public broadcaster ZDF, Macron said "a return to national interests" was the "worst option" for the continent.
"The populists are on the rise and they are being strengthened by our inability to help the middle class succeed," he said.
Macron stressed that Europe needed work together to offer "perspective and progress" to each individual.
The ZDF interview comes just days after the French president set out his vision for the EU, saying all the member countries must forge a common path.
His agenda included plans to give the 19-member eurozone a finance minister, budget and a parliament independent of the 28-country EU's existing 750-seat transnational legislature.
His proposals for the future of the EU met with a generally positive but also non-committal response of EU leaders.
Read more: Emmanuel Macron's EU vision meets Angela Merkel's realities
Growth to counter inequality
Macron on Thursday stressed on the need to push economic growth in the region as a means to counter growing social and economic inequality.
"I believe all divisions in Europe stem from an inability to deal with the future," he said. "We doubt ourselves and curl up into a ball."
He added that the past 12 years in Europe have been characterized by self-doubt and what he said could almost be called a "European civil war." Macron said the EU member have rather chosen to work for national interests.
"We lack mutual solidarity and sometimes the necessary responsibility – some have not reformed, the others did not show solidarity," he said.
ap/sms (dpa, ZDF)