The lessons of the First World War and the current crisis in the Crimea reveal "the folly of nation states" and the danger of concentrating defence in their hands, North East Scotland MSP Jenny Marra said.
She rejected criticism of the "centralising" force of Brussels and dismissed calls for an in/out referendum on the EU, insisting it should have more powers, particularly on defence.
"Anyone who has been watching the coverage following the media's reflections on the precipitation towards the First World War 100 years ago would see the folly of nation states," she said at a Scottish Labour Party conference fringe event in Perth.
"Defence forces constantly being in the power of nation states' hands is quite a dangerous place to be.
"The EU, looking to the future, perhaps a single defence force is certainly an idea that appeals to me, having been a Labour member who marched outside my own party's conference in 2003 against the invasion of Iraq.
"The idea of taking defence out of the hands of nation states appeals to me.
"I know it's not necessarily a view that is commonly shared but I think it's one in 2014, we should reflect on, certainly with the awful situation that is happening in the Crimea."
Ms Marra is seen as a rising star within the party, scoring a personal victory this week when her Member's Bill on human trafficking was adopted by the Scottish Government.
She rose from party spokeswoman on Europe, based in Brussels and Strasbourg, to second on the party's North East Scotland regional list in 2011, behind established MSP Richard Baker.
She was soon elevated to the party front bench and holds two portfolios. as shadow minister for youth employment and deputy shadow finance minister.