Gay Anglican Jayne Ozanne and LGBT groups have written to the government asking it to bring forward legislation to ban so-called conversion therapy.
The letter is backed by Stonewall and the Ban Conversion Therapy Coalition, which Ozanne chairs, among other organisations.
The government promised to ban so-called conversion therapy five years ago. In January, the government said it was preparing to publish a draft bill.
The LGBT campaigners have written a joint letter to Prime Minister Rishi Sunak, women and equalities minister Kemi Badenoch, and Minister for Equalities, Stuart Andrew.
In the letter they said they wanted the government to "publish the long-awaited legislation" in April and "end all forms of this appalling abuse".
"Time is now running perilously short for this legislation to be passed before the end of the fourth session, particularly given your desire for pre-legislative scrutiny," the letter says.
"Whilst we agree this important legislation requires careful scrutiny, we would suggest that the sooner this Bill comes before Parliament, the longer both Houses will have to carefully consider and debate it."
Ozanne said, "We urgently need a robust ban on these harmful practices - we have waited long enough! There can be no more excuses nor delays.
"No more ifs, no more buts and certainly no more loopholes. Far too many lives have already been ruined - we cannot afford to drag this out any longer!"
Last month, Badenoch, addressing the Women and Equalities Select Committee, refused to give a date for the legislation.
Evangelical Christians have expressed concerns that the ban will criminalise ordinary church practices like prayer, preaching and pastoral counselling.
The Evangelical Alliance received assurances from former prime minister Boris Johnson that prayer would not be criminalised.
In an interview with the Religion and Media Centre last month, Evangelical Alliance CEO Gavin Calver reiterated the organisation's opposition.
He said that introducing a ban could have "unintended consequences" and that churches "should be free" to pray for people with unwanted same-sex attraction.
