Dr Peter Ammon is leaving his post, but took the opportunity to hit out at the Brexit decision, branding it a “tragedy”.
He claimed the UK would lose its influence internationally once it left the bloc and the Government would be unable to secure the trade deal it wanted with the EU.
Laughing off the view Germany dominated the EU, he said the decision to leave by some Brexiteers came from a national image based on Britain’s wartime fight against his nation.
He told the Guardian: “History is always full of ambiguities and ups and downs.
“But if you focus only on how Britain stood alone in the war, how it stood against dominating Germany, well, it is a nice story, but does not solve any problem of today.
“I spoke to many of the Brexiteers, and many of them said they wanted to preserve a British identity and this was being lost in a thick soup of other identities.
“Obviously every state is defined by its history, and some define themselves by what their father did in the war, and it gives them great personal pride.”
And he warned the country’s ambitious hopes of a bumper trade deal beyond the confines of the EU were doomed and would lead to people blaming Brussels instead of than their own decision to leave the powerful trading bloc in the first place.
Dr Ammon said: “The idea that there is in future a bonanza or a pot of gold somewhere through free trade agreements with third parties seems fanciful.
“The idea that you leave the customs union because the customs union would forbid you from entering separate free trade agreements with third countries concerns me.
“What happens if, as is likely, Britain comes back from these negotiations and says ‘What I have got here is not very spectacular’?
“What I fear is there will be a blame game for this non-success. It will be explained as something the Europeans have done.”
And he claimed people’s concerns about immigration from the EU no longer had any foundation and they would be better off worrying about who will look after them in hospital.
He said: “I have heard officials here say we are now at zero net migration from Europe so the issue seems to have gone.
“Instead people are desperate for plumbers and health service staff from eastern Europe, so from the outside, you wonder why people now worry.
“I would worry more about the shortage of staff.”
It comes as Mrs May faces criticism from hardcore Brexiteers in her own party who are unhappy at the way negotiations have gone.
Backbenchers such as Jacob Rees-Mogg, who style themselves as the true voice of Leave voters, have hit out at plans for the two-year transition period.
EU Brexit negotiator Michel Barnier today stressed EU law would have to apply in the UK during the transition, including any changes that were agreed during that period, as Britain would continue to enjoy the full economic benefits of EU membership.
Speaking in Brussels after EU foreign ministers formally adopted the guidelines for negotiations on a transition, he said: “During that period the decisions will apply and the UK must acknowledge and accept these rules of the game from the outset.”
Mr Barnier insisted that Britain could not have a la carte access to the single market.
He said: “During transition the UK will continue to take part in the single market, to take part in the customs union.
“It will continue to have all the economic benefits therefore it must also apply all the EU rules. The single market cannot be a la carte.”