Figures reported by The Sunday Times show Oxfam recorded 87 incidents a year ago, Save the Children 31 and Christian Aid two, while the British Red Cross admitted there had been a "small number of cases of harassment reported in the UK".
Another involved an assault on a teenage volunteer by a staff member in a charity shop in Britain, she said.
Evans also told media of a survey conducted during her 2012-2015 tenure which exposed a "culture of sexual abuse" in some Oxfam offices.
McCarthy noted that humanitarian workers often put themselves at great risk in order to do their work and are "motivated by a desire to help people in crisis situations". I asked repeatedly: we need more resource for this and it wasn't forthcoming.
Oxfam is battling the fallout from revelations some of its staff engaged sex workers while delivering aid after the 2010 natural disaster in Haiti.
Among 12 allegations of abuse over two years, one shop manager allegedly attempted to force a young volunteer to drop charges against an adult male who apparently carried out an indecent assault.
Her email to Goldring, shared with Channel 4, said: "Having a concern discussed at LT (leadership team) with feedback from the chief executive can go a long way to effecting positive change".
She said a meeting was held to discuss her concerns about widespread abuse but no action was taken until previous year.
"Thanks to Helen's work we have introduced a whole range of measures to improve how we deal with safeguarding issues".
Bain said CAFOD is joining an initiative with other UK-based overseas development agencies and the Charity Commission, the government department that regulates registered charities in England and Wales, to strengthen cross-sector information sharing and protection of vulnerable people.
She also wrote to all United Kingdom charities working overseas to insist they give her specific assurances that they have reported everything untoward to the relevant authorities.
Mark Goldring, who has led Oxfam since 2013, has come under pressure as the organisation reels from a prostitution and sexual abuse scandal.
'In the 21st century, it is utterly despicable that sexual exploitation and abuse continues to exist in the aid sector.
Reuters was unable to reach any of the Oxfam staff who worked in Haiti at the time.
The deputy chief executive of the United Kingdom branch of the leading charity resigned on February 12.
"However, the issues revealed in recent days are shocking and unacceptable". If they are children, they should be charged in front of the courts here because he's broken the sex tourism laws.
European Commission officials have said they are also considering pulling £29 million in funding from Oxfam.
The EU on Monday also warned that the bloc would withhold funding if charities breached ethical standards.
In 2011 it added £1.5 million to Oxfam's Haiti quake fund.
"The Commission has concerns that Oxfam may not have fully and frankly disclosed material details about the allegations at the time in 2011, its handling of the incidents since, and the impact that these have both had on public trust and confidence", the statement said.