The Charity Commission is looking into what it has called "deeply distressing" allegations of homophobia and controlling behaviour at a Sheffield-based charity that supports victims of modern slavery.
City Hearts, which was set up in 2005 by the Hope City Church in Sheffield and had an income of £2.7m in the year to the end of March last year, provides supported accommodation and a structured recovery programme for vulnerable women, plus support and accommodation for men, women and families rescued from sexual and labour exploitation in north-east and south Yorkshire.
Channel 4 News spoke to women who said they felt they were being controlled by the charity, including one who said she had been subjected to homophobic treatment.
Another former employee of the charity said she had been responsible for managing a safe house at the age of 20 with inadequate training or experience.
A Charity Commission spokeswoman said: "These are deeply distressing allegations that raise serious regulatory concerns and might point to failings on the part of the trustees of the charities in question.
"We have made clear that trustees must ensure their charities are safe places for all who come into contact with them, especially those who may be at risk or vulnerable as a result of their experiences or circumstances. We are assessing Channel 4’s findings as a matter of urgency and require the trustees to respond to our questions.
"We are also engaging with the charity’s funder, the Salvation Army, to ensure it is carrying out appropriate due-diligence checks on the partners it works with."
The Salvation Army, which runs the Home Office contract to provide support for the victims of modern slavery, has funded City Hearts to provide services.
A spokeswoman for the Home Office said it was "deeply concerned" by the allegations and was working with the Salvation Army to look into the claims.
"This includes seeking immediate assurance from the Salvation Army that all those receiving support as victims of modern slavery are receiving the right standard of care," she said.
A spokeswoman for the Salvation Army said: "The support provided to the people identified to us by Channel 4 was given outside of the specialist support subcontracted to City Hearts by the Salvation Army.
"However, in light of these allegations we are looking into this situation, including bringing forward a regular safeguarding inspection of City Hearts, which we undertake with all our subcontractors.
"In the absence of any official independent inspection regime, the Salvation Army has drawn on our existing auditing infrastructure and long-standing expertise and experience in delivering high-quality services to vulnerable people."
She said the charity performed annual audits relating to safeguarding and information security, including visits to safe houses, and had a system of monthly inspections of client support plans.
Edward Newton, managing director of City Hearts, said the charity "seeks to uphold the highest standards of excellence and diversity" and was "very disappointed to hear the allegations" against it.
"We are of course investigating these matters and in the meantime it would be inappropriate for us to comment publicly, especially in relation to the individuals involved," he said.
"We will in any event review our policies and procedures to try to make sure we are as supportive and protective as we can be in supporting people whose lives have been so badly harmed by the evil of modern slavery."
The charity had helped about 4,250 people to go on to lead fulfilling, independent lives, said Newton.