A public consultation will be opened before a ban on so-called conversion therapy, the BBC understands.
“Conversion therapy” attempts to change someone’s sexual orientation or gender identity, according to NHS England.
The consultation will consider religious freedom and how to protect professionals, including therapists, say government sources.
The proposed ban on conversion therapy in England and Wales will be announced in the Queen’s Speech on Tuesday.
Campaigners say ministers must act fast and bring in a ban across all settings.
In practice, conversion therapy means trying to stop or suppress someone from being gay, or from living as a different gender to their sex recorded at birth, NHS England says.
It and many other professional bodies have warned all forms of conversion therapy are “unethical and potentially harmful”.
The practice can take many forms, some of which – like “corrective” rape – are already illegal.
In 2018, Theresa May’s government promised to end conversion therapy as part of its LGBT equality plan.
Last summer, Prime Minister Boris Johnson said plans for a ban would be brought forward.
But it has emerged that a “short” consultation will be held before the legislation is finalised, asking the public and interested parties how best to address the problem.
The ban is set to include both sexuality and gender identity.
But sources say the consultation will examine how to ensure professionals, such as therapists, can still help people fully explore their gender identity.
The government also wants “legitimate forms of pastoral support” to be allowed to continue.
In April, Mr Johnson wrote to the Evangelical Alliance, which represents 3,500 churches, to reassure the group that adults will still be able to “receive appropriate pastoral support (including prayer)… in the exploration of their sexual orientation or gender identity”.
Peter Lynas, the group’s UK director, said it welcomed the consultation process.
“We want to avoid the situation were a person can be accused of conversion therapy for praying with someone who freely chooses and asks for prayer,” he said.
But Jayne Ozanne, a former government equality adviser who was subjected to conversion therapy, says religious practices must be included in the ban.
“They have consulted long enough, now it is time to act and bring forward legislation that protects everyone from this inhumane and degrading abuse,” she said.
Stonewall’s chief executive Nancy Kelley said a “full and comprehensive bill” must look to ban conversion practices “in all forms and in all settings”.
A government source said: “This will do exactly what we promised to do – banning LGBT conversion therapy in legislation and stamping out the last vestiges of this heinous practice.”
About 5% of the 108,000 people who responded to a 2018 LGBT government survey said they had been offered some form of conversion therapy, while 2% had undergone it.
More than half said it was conducted by a faith group, while one in five received it from healthcare professionals.
The ban will apply to England and Wales, and a support fund for victims of the practice will also be made available. Northern Ireland has passed a non-binding motion calling for a ban on gay conversion therapy “in all its forms”.
The Scottish government “fully supports moves by the UK government to end conversion therapy”, a spokesperson said.