The EU is facing an existential crisis as well as a health crisis if it fails to unite to overcome the economic consequences of the coronavirus pandemic, a French minister has said.

France’s Europe minister, Amélie de Montchalin, said the “credibility and usefulness” of the EU rested on its collective response to the health crisis and called for unity to be “more than just a slogan”.

She said many member states were cooperating on research, vaccines and the treatment of patients, but she called on European leaders to overcome “selfishness and fear” and show solidarity to avoid an economic catastrophe.

“If European unity is just a slogan then we have a problem. We need to be united not just with research with the vaccines, but the measures we are taking to ensure the economic mire is not too deep,” Montchalin told France Inter radio.

“We need to prepare together how to get out of this crisis and relaunch [economies]; we need to prepare for afterwards and show that we are efficient because we are together.”

She added: “Can we continue to work at 27 if there are those who are not showing solidarity? Those who don’t want to show this solidarity need to consider their position. EU members will need to ask how they make decisions as a group of 27 if they cannot decide on financial support for coronavirus-hit nations.”

Earlier, Jacques Delors, 94, a former European commission president, issued a rare statement saying divisions between northern and southern member states during a European council meeting on Thursday pointed to “mortal danger” for the bloc.

A rift emerged after the Dutch finance minister, Wopke Hoekstra, reportedly called for an investigation into why some EU member states lacked the financial capacity to weather the coronavirus crisis.

Portugal’s prime minister, António Costa, described Hoekstra’s comments – which appeared to be directed at southern European members – as “repugnant”.

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Costa is among those who have said the pandemic could pose an existential threat to the EU. “If the EU wants to survive, it’s unacceptable for any political figure – wherever they’re from – to give that kind of answer given the pandemic we’re living through,” Costa said.

Spain’s prime minister, Pedro Sánchez, issued a similar warning on Friday. “We’re facing the worst crisis of this generation,” he said. “The future of the European project is at stake and we need to choose between individualism and a coordinated, supportive EU. We are profoundly pro-European and we are seeking a common response to this emergency.”

Sánchez went further on Saturday night when he told Spaniards: “It’s Europe’s time to act. Europe is at risk.”

Spain’s foreign minister, Arancha Gónzalez Laya, also responded bluntly to Hoekstra on Twitter. “We’re all in the same European boat,” she wrote. “We’ve hit an iceberg and now we’re all running the same risks. There’s no time for discussions about supposedly first and second class citizens. This isn’t the time to defraud our citizens.”

Gónzalez Laya reminded the Dutch minister that “this is 2020, not 2008”, adding: “The pandemic is affecting all of us. It’s not about the failure of one sector or one geographic region.”