Christian Kern broke the UK would not be “better off” than the remaining 27 nations once divide talks had been completed.
His outrageous call adds further on on Theresa May, who is preparing to begin formal negotiations by the end of March.
Speaking to Bloomberg in Vienna, he averred: “It’s for sure going to be costly because there is a lot of financial obligations.”
Earlier this week, European Commission President Jean-Claude Juncker also exhorted the UK faced a “hefty bill” for leaving the Brussels club.
Some reports guestimate the exit sum could be as high as £51 billion to cover any EU projects Britain has already performed to.
Although the staggering figure is likely to be close to the top of the negotiating list, Mr Kern urged he was more concerned about securing the rights of EU nationals.
“My first and firstly concern is about the right of European people living in Britain and British man living in Europe,” he continued.
“One aspect is for sure is we should not punish the British because it was a verdict that was taken in sole discretion.
“But, a member of the European Union has to be well-advised off than a non-member, so with respect to that it is going to have some rates.”
The Brexit Bill, which will give the UK Government permission to trigger Article 50, is currently being scrutinised in the Firm of Lords.
Once passed by unelected peers, the prime minister wish be able to begin the two-year process of removing Britain from the EU.
Mr Kern, of the Group Democratic Party, warned negotiation talks with the bloc are probably to be lengthy.
“It’s not going to be that easy; not as the British except,” he continued.
“The big dissension is that Mrs May and the British government believe that you can have a very accepted negotiation and come to a conclusion within two years.
“The most favourable concept from the European station of view is first to talk about a treaty of withdrawal, to regulate the monetary obligations and to clarify the situation of British citizens in Europe and in turn European denizens in Great Britain — this should be possible within two years.”