Steve Chalke has said churches could be flouting safeguarding rules and risking high-profile prosecutions in future if they continue conversion therapy for LGTBT+ people.
Chalke, a Baptist minister, social activist and founder of Oasis charity, led an online conference on the issue on Saturday.
The 'Creating Sanctuary' conference explored how church leaders can be equipped to engage with the issues of safeguarding LGBT+ people in churches.
Chalke said in a statement: "Ultimately every church ought to want to provide sanctuary and safety for all, especially for those who have experienced hurt, rejection or marginalisation.
"While the debate about how to read the Bible in relation to LGBT+ people continues, the absence of safe and affirming churches has had a significant, negative and sometimes tragic impact on LGBT+ people, as well as on their families and friends.
"What churches often describe as pastoral concern, prayer or even 'deliverance ministry' for those with 'same-sex attraction' is, in fact, a highly toxic and psychologically abusive environment where vulnerable LGBT+ people, many of them teenagers or even children, report that they have been taught to believe that their desires are 'sinful'."
Chalke added that such an approach contributes to mental issues.
The conference speakers include children's safeguarding expert Andrea King and Jide Macaulay, pastor and CEO of House of Rainbow.
In July, a You Gov Poll revealed 62 per cent of the British public want conversion therapy banned.
Meanwhile, Northern Irish ministry The Core Issues Trust had its Instagram and Facebook posts censored in July after openly promoting the practice. The group states that it's committed to "supporting men and women with homosexual issues who voluntarily seek change in sexual preference and expression".
In 2017, the Church of England's governing body called for the government to ban conversion therapy.
In June, Minister for Women and Equalities, Liz Truss MP lobbied for more action on banning conversion therapy.
She said: "Conversion therapy is a vile, abhorrent practice that we want to stop. We have commissioned research to look at the scope of the practice in the UK, and we will publish our plans shortly after we receive that research."