Story highlights French President attacks Trump's comments on Europe

Largest party in European parliament calls Trump's likely pick for EU envoy "hostile"

Valletta, Malta (CNN) EU leaders, led by French president Francois Hollande, have denounced recent attacks on Europe by Donald Trump as they met for a summit to debate the future of the union.

Hollande described Trump's statements as "unacceptable", and German Chancellor Angela Merkel called on the EU to press ahead with its own plans whatever the US says.

EU leaders have been rattled by Trump's comments on Europe and the NATO transatlantic alliance. He has voiced his support for Britain's departure from the EU, criticized European refugee policies and called NATO "obsolete".

Hollande hit out at Trump as he arrived at the informal summit on the future of the EU in Malta. "There are threats, there are challenges. What is at stake is the very future of the European Union," he said.

President of the European Union Jean-Claude Juncker, center left, and British Prime Minister Theresa May at the Malta summit.

"It is unacceptable that there should be, through a number of statements by the US President, pressure on what Europe should be or what it should no longer be."