Ermotti was appointed Saturday to replace former CEO Oswald Gruebel, who stepped down 10 days after the scandal broke, saying her bore responsibility for the massive loss.
London-based trader Kweku Adoboli, 31, was arrested Sept. 15 and charged with fraud and false accounting.
“The unauthorized trading incident has deeply frustrated all of us,” Ermotti told UBS bankers in the memo.
“It has dealt us a severe setback in our efforts to regain trust and make UBS the leading bank for our clients.”
Under Gruebel’s 2 1/2-year leadership, UBS had begun to recover from massive subprime losses and an embarrassing US tax evasion case, though it was still struggling to fully re-establish its reputation.
“We will not allow this incident to define us, nor will we permit it to undermine the achievements you made under Ossi’s leadership in the past two-and-a-half years,” said Ermotti, referring to his predecessor by his nickname.
He also urged staff to “now summon our collective strength to demonstrate what UBS stands for.”
Swiss media have widely tipped Ermotti, 51, to become the bank’s new permanent CEO. But questions have been raised about some of his interests outside the bank, including his involvement on the board of companies in his home canton (state) of Ticino, Switzerland’s Italian-speaking south.
On Thursday, UBS issued a short, after-hours statement accusing the media of publishing “damaging, untrue statements” about Ermotti’s outside engagements.
The bank said its board was aware of the engagements and had approved them, but that he would now lay them down “in a quick but orderly manner” to focus on his job as interim CEO.
UBS didn’t specify what mandates Ermotti held, or with which companies.
