Charlotte Galpin, a German and European Politics lecturer at the University of Birmingham, said full sovereignty for nation states was over.
Speaking as part of The Brexit Panel at the University of Birmingham, the professor said Britain now needed to sort out its relationship with the European Union and rest of the world.
"What is happening is that both parties are telling the public that we can achieve things in these negotiations that are simply not possible,” she said.
Charlotte Galpin said sovereign nations were no longer possible
Both parties are telling the public that we can achieve things in these negotiations that are simply not possible
"I think that this also completely kind of ignores what is really at stake.
"The fundamental issue is that we live in a world where sovereignty completely bounded to the nation states is not possible, so we should be talking about what kind of country we want to be and what kind of relationship we want to have with the world and with the rest of Europe."
Meanwhile, Brexit and Donald Trump’s election are being viewed as an "opportunity" in European capitals to increase military cooperation, an expert on EU affairs said.
Britain’s decision to leave the European Union and the election of the isolationist US president have fundamentally changed Europe’s security situation, Charles Lichfield, Europe Associate at the Eurasia Group said.
May meets Juncker and Barnier at Number 10 Wed, April 26, 2017
Theresa May hosted European Commission President Jean-Claude Juncker and chief negotiator Michel Barnier at Downing Street for the first face-to-face talks since she triggered the two-year process of withdrawing from the EU
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Prime Minister Theresa May greets European Commission President Jean-Claude Juncker ahead of a working dinner at 10 Downing Street, London
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Mr Lichfield told Al Jazeera: “There's some concern but it also is seen as an opportunity to bolster EU defence cooperation.
“[Germany, Italy and France] are the countries that I think are most enthusiastic.
“Britain was, for a long time, much more reluctant and now that it is leaving the EU this is seen as an opportunity in Western Europe to actually go further with EU defence, although they haven't been very precise for the moment.”