The charity says it is taking action following a “very small number of safeguarding incidents”.
Samaritans says it has introduced new safeguarding measures after volunteers met vulnerable callers for sex.
The charity, which offers a helpline to people in distress, will reportedly monitor calls in future to prevent inappropriate relationships.
The Telegraph found incidents of middle-aged men using their position to meet up with female callers for sex.
The charity told the BBC it did not dispute that a “very small number of safeguarding incidents” had occurred.
Samaritans chief executive Julie Bentley said the “extremely rare” incidents had been identified and that swift and appropriate action had been taken.
According to the Telegraph, a memo to volunteers said 44 serious incidents had occurred since 2017.
Ms Bentley said Samaritans’ 20,000 volunteers provided vital emotional support to anyone who is struggling, 24 hours a day, 365 days a year.
Volunteers on the charity’s telephone service have answered more than 13 million calls in the four years from January 2017, she said.
“Running any national service on this scale means that, on extremely rare occasions, high standards are not always met and from the millions of calls answered, a very small number of safeguarding incidents were identified,” said Ms Bentley.
“Our robust investigation procedures meant these incidents were handled swiftly and appropriate action taken.
“Any safeguarding matter is one too many and as such we review our practices on an ongoing basis and have introduced further measures as part of our commitment to delivering a consistently high-quality experience for our callers.”
Incidents are investigated by the charity’s Serious Safeguarding Panel and are reported to the Charity Commission, Samaritans said.
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