The government has announced it is reviewing all its work with Oxfam, after the charity was accused of covering up the use of prostitutes by its aid workers in Haiti.
The Department for International Development (DFID) said the charity had to answer "serious questions".
Oxfam received nearly £32m from the DFID in the last financial year.
The UK-based charity has denied a cover-up and said it publicly announced an inquiry into the claims in 2011.
It said the behaviour of some of its staff had been "totally unacceptable".
Four staff members were dismissed and three, including the country director, were allowed to resign before the end of the investigation, Oxfam said.
The director was Roland Van Hauwermeiren, who The Times alleges used prostitutes at a villa rented for him by Oxfam.
The staff had been in Haiti as part of the relief effort in 2011, following the devastating magnitude 7.0 earthquake that killed more than 200,000 people in 2010.
The government comes amid fresh allegations in The Times that the charity failed to alert other aid agencies about the staff members' behaviour. Mr Van Hauwermeiren went on to work elsewhere in the sector.
Oxfam has yet to comment on the latest claims.
'Lack of judgement'
A DFID spokesman said: "The way this appalling abuse of vulnerable people was dealt with raises serious questions that Oxfam must answer."
He said the department acknowledged that hundreds of Oxfam staff had done nothing wrong, "but the handling by the senior team about this investigation and their openness with us and the charity commission showed a lack of judgement".
"We have a zero tolerance policy for the type of activity that took place in this instance, and we expect our partners to as well," the spokesman said.
"We often work with organisations in chaotic and difficult circumstances.
"If wrongdoing, abuse, fraud, or criminal activity occur we need to know about it immediately, in full."
International Development Secretary Penny Mordaunt had requested a meeting with Oxfam's senior team "at the earliest opportunity", the spokesman said.
Andrew Mitchell, who was international development secretary in 2011, said DFID "must be sure that there is zero tolerance for this sort of thing".
An Oxfam spokeswoman said in a statement on Friday: "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.
"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."
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 told Newsnight.
"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".