A day after French President Francois Hollande labeled Barroso's new job as "morally unacceptable" because he would be advising the bank on Brexit issues, Goldman stressed that the recruitment was done prior to the June 23 British referendum.
"That decision had nothing to do with the outcome of the Brexit vote," the bank said in a statement.
"Indeed, we began our discussions at a time when the prevailing view was that the Remain campaign would succeed, an outcome we would have preferred and publicly supported."
Barroso headed the executive arm of the 28-nation EU from 2004 to 2014. European politicians say that his inside knowledge of EU affairs, in light of Britain's shock vote to break with the union, could lead to potential conflicts of interest.
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The US bank stressed today that Barroso would help advise its clients in Europe and around the world on a range of issues.
Hollande's condemnation was the strongest yet. Barroso would be assisting a bank which "advised the Greek government and dressed up the deficit figures it gave to the European Union several years ago," he said.
France's Minister for Europe Harlem Desir said on Wednesday Barroso was "helping anti-Europeans".
"I solemnly appeal for him to give up the post," Desir told the French parliament.