A European Union army is needed to face up to Russian antagonism, according to EU President Jean-Claude Juncker.
The suggestion by the former Luxembourg president in an interview has set alarm bells ringing in Britain.
Juncker told Welt am Sonntag magazine an EU army was necessary because the organisation was not being taken "entirely seriously".
Alarms have been triggered by fighting between Russia and EU member state Ukraine in a territory dispute.
Juncker said military might would send a message that the EU was serious about "defending values".
"You would not create a European army to use it immediately," he told the newspaper in Germany in an interview published on Sunday (8 March).
"But a common army among the Europeans would convey to Russia that we are serious about defending the values of the European Union.
"Such an army would help us design a common foreign and security policy."
Calls for an EU army were condemned by Conservative MEP Geoffrey Van Orden.
"This relentless drive towards a European army must stop. For Eurocrats every crisis is seen as an opportunity to further the EU's centralising objectives," he said.
"However the EU's defence ambitions are detrimental to our national interest, to Nato, and to the close alliances that Britain has with many countries outside the EU – not least the United States, Gulf allies, and many Commonwealth countries."