One of the UK's biggest charities has denied allegations it covered up the use of prostitutes by its aid workers in Haiti.
Responding to a report in The Times newspaper, Oxfam admitted that the behaviour of some of its staff had been "totally unacceptable".
But the charity said it had publicly announced an investigation into the allegations when they surfaced in 2011.
Several senior aid workers were dismissed following the investigation.
"The behaviour of some members of Oxfam staff uncovered in Haiti in 2011 was totally unacceptable, contrary to our values and the high standards we expect of our staff," a spokeswoman said in a statement.
"Our primary aim was always to root out and take action against those involved and we publicly announced, including to media, both the investigation and the action we took as a result."
Oxfam said four members of staff were dismissed and three, including the country director, were allowed to resign before the end of the investigation.
The director was Roland Van Hauwermeiren, who The Times alleges used prostitutes at a villa rented for him by Oxfam.
At the time, the charity said he had left because of serious breaches of its code of conduct.
But reports say Oxfam failed to specify the men had been using prostitutes. The charity denies this, and says it disclosed sexual misconduct to the charities regulator.
Dame Barbara Stocking, who was the head of Oxfam in 2011, told the BBC that the charity had a long record of having a very good code of conduct.
"Of course when that happened we looked at it all again," she said. "New whistleblowing procedures were put in place, [there was] more safeguarding work and more training. You just have to have eternal vigilance."
She said Oxfam often worked in very difficult locations "where the rule of law isn't going on".
UK culture secretary Matt Hancock told the BBC that the allegations were "abhorrent and completely unacceptable".
"Oxfam must now provide the Charities Commission with all the evidence they hold of events that happened in Haiti as a matter of urgency," he said.
"Charities must ensure that they have the highest standards of transparency and safeguarding procedures in place to protect vulnerable people and maintain the trust of the public."
A spokeswoman for the Charities Commission said: "In August 2011, Oxfam made a report to the Commission about an ongoing internal investigation into allegations of misconduct by staff members involved in their Haiti programme.
"At the time, and based on the information provided, we were satisfied that the trustees were handling matters appropriately and did not have regulatory concerns."
The spokeswoman added: "We will expect the charity to provide us with assurance that it has learnt lessons from past incidents".
Haiti became the world's first black-led republic and the first independent Caribbean state when it threw off French colonial control and slavery in the early 19th century.
Political instability and a spate of natural disasters in recent decades have left Haiti as the poorest nation in the Americas.
A devastating earthquake, the worst in more than 200 years, hit the country in 2010.
The magnitude 7.0 quake killed more than 200,000 people and caused extensive damage to the country's infrastructure and economy.