The Mail on Sunday's front page this week alleged that a senior figure at the Royal Commonwealth Society was allowed to "quietly resign" after it was discovered he had had encounters with sex workers.
It said the incident in 2009 cast doubt over Sriskandarajah's suitability to clean up Oxfam in the wake of last week's highly critical commission report on the charity's handling of the Haiti safeguarding scandal.
A commission spokeswoman told Third Sector yesterday: "We do not have a record of the Royal Commonwealth Society having reported this matter to the commission at the time.
"We will be engaging with the charity to assess its handling of these serious allegations.
"The public rightly expect charities to demonstrate the highest standards of conduct, behaviour and attitude. That includes full and frank reporting if things do go wrong, as well as demonstrating that they are handling matters appropriately."
Greg Munro, chief executive of the society, said he was appalled to discover the matter had not been reported to the commission.
Munro said none of the charity's current staff or trustees were involved with the organisation in 2009 and it was "principally" up to those running it a decade ago – including Sriskandarajah – to provide answers.
He said: "I would like the trustees and chief executive at the time to provide full disclosure of what happened."
Munro said the charity would check board minutes from 2009 to see if the matter was reported.
He added that it would also contact Sriskandarajah and trustees at the time to request assistance.
"We don't condone this behaviour at all," he said. "We are a very small organisation now compared with then and we have got caught up in the crossfire, but that's no excuse. We will cooperate fully with the commission."
Sriskandarajah issued a statement on Monday saying the matter occurred just weeks after he joined and was "rightly" dealt with by trustees.
"I was not involved in, or party to, any decisions relating to the resignation," he said.
An Oxfam spokesman declined to comment further.