Haiti's government has withdrawn the Oxford-based charity's right to work in the country.
Oxfam GB was plunged into crisis in February when it emerged some of its workers engaged in "sex parties" with prostitutes in the aftermath of 2010's earthquake in the Caribbean country.
The Haitian government said the decision to ban Oxfam GB from working in the country was due to a violation of laws.
Oxfam said it was disappointed but understood the decision, and added it would continue to work in Haiti through affiliate members in Italy, Spain and the Canadian province of Quebec.
"The behaviour of some former Oxfam staff working in Haiti following the 2010 earthquake was completely unacceptable. We have apologised to the government and the Haitian people for what happened," a spokeswoman said.
The former head of Oxfam's operations in Haiti admitted having a sexual relationship with a woman he helped in the aftermath of 2010's earthquake but denied using prostitutes.
Roland van Hauwermeiren wrote an open letter in which he said he was "deeply ashamed" by aspects of his behaviour.
In February, the head of Oxfam International Winnie Byanyima described the sexual exploitation allegations as a "stain" on the charity "that will shame us for years" as she announced plans to try to stamp out abuse in the organisation.
Mark Goldring, the former chief executive of Oxfam GB, announced he would be leaving his post at the end of the year after navigating the charity through the scandal.
After apologising to the Haitian ambassador in the aftermath of the allegations, he struck a less conciliatory tone in an interview with the Guardian days later in which he claimed critics were "gunning" for his organisation and suggested no-one had "murdered babies in their cots".
Last month, he said: "Following the very public exposure of Oxfam's past failings, we have redoubled our efforts to ensure that Oxfam is a safe and respectful place for all who have contact with us.
"We are now laying strong foundations for recovery.
"I think that this journey will best be led by someone bringing fresh vision and energy and making a long-term commitment to see it through."